JUDGMENT S.K. Mookherjee, Acting C.J.: The present appeal is directed against judgment of a learned single Judge, dated 31st January, 1996, passed in a writ proceeding, being C.O. No. 12332 (W) of 1990. Shortly, the facts are that at the instance of appellant No.2, a School in the name of 'Calcutta Dock Labour Board Primary School' having three units, Hindi, Bengali and Urdu, was granted recognition on or about 19th October, 1985. The terms on which such recognition have been granted included, inter alia, the following terms :- Accepted scales of pay and D.A. in respect of approved teachers will be provided to the teachers of the Schools. 2. The School was admittedly run in a room, which actually was staff quarter of respondent No.5/appellant No.1. The teachers of the school, who were allegedly appointed by an Ad hoc Committee constituted by the appellant No.1, were paid a lump sum monthly salary of Rs. 500/- each. The writ application in question was moved, praying for reliefs, inter alia, for payment of the teachers at the same scale of pay and other allowances, including arrears, as admissible to the Primary Teachers of the recognised Primary Schools on and from 1.1.1996. From the side of the respondents, affidavit-in-opposition had been filed, inter alia, controverting the correctness of the statements made in the writ application and, in particular, asserting that the appellants were in no way statutorily responsible to bear the financial burden with regard to the School. 3. The learned Trial Judge, by the impugned order, allowed the writ application, inter alia, upon finding that the assurance held out by the appellants justifiably gave rise to a legitimate expectation that the appellant No.1 would bear the financial liability, which would otherwise have been the liability of the State Government. 4. The submissions, which have been made before us by the learned Counsel representing the contesting parties, appear to give rise to the following questions:- (i) Whether the assurance and conduct of the appellant no.1, or its officers could be said to have constituted a promise as to estop the appellants from denying the financial liability of paying the petitioners in conformity with the scale of pay enjoyed by the recognised teachers of the Primary Schools. (ii) Whether such assurance and the conduct could be said to have given rise to legitimate expectation. 5. (ii) Whether such assurance and the conduct could be said to have given rise to legitimate expectation. 5. The theory of promissory estoppel to have been firmly settled by different decisions of the Apex Court. In the case of M.P. Sugar Mills Company Limited vs. The State of Uttar Pradesh and Ors., reported in AIR 1979 SC 621 , the Court, while laying down that the doctrine of promissory estoppel which is otherwise known as 'requisite estoppel', 'quasi estoppel' and 'new estoppel' is basically a doctrine of equity and, though, even a Government is not permitted to repudiate a liability arising out of its promise on which the other party might have acted even without detriment, laid down also the said doctrine cannot be enforced to compel the Government or even a private party to do an act prohibited by law. The same principle has been reiterated in the cases of Union of India vs. Godfrey Philips, reported in AIR 1986 SC 806 and P. G. Eshwarappa vs. M. Rudrappa, reported in 1996 (6) SCC 96 . In the instant case, it has been very strenuously urged, on behalf of the appellants that the Calcutta Dock Labour Board has no statutory obligation nor any right to incur any expenditure for the purpose of an object, which does not fall within the scope of its authority, as envisaged in Calcutta Dock Workers (Regulation of Employment) Act, 1948 and the Scheme of 1970 framed thereunder. Subsection (2) of s. 3, by cl. (gg), provides that a scheme may be framed for welfare of the officers and other staff of the Board; Clause 7 of the scheme describes the functions of the Board; Sub-clause (2) of the said cl. 7 lays down that the income and property of the Board may be applied towards the objects of the scheme, including, amongst others, welfare measures of the workers or for the staffs of the Board. 6. Section 21 of the Dock Workers (Safety, Health and Welfare) Act, 1986 by cl. (w) lays down that regulations may provide for "sanitary, washing and welfare facilities". The term welfare has not been defined but in view of its juxtaposition with other terms, in our opinion, the interpretation of the term should be made ejusdem generis, and, accordingly, cannot be stretched to include educational facilities. Section 3 of the Dock Workers Regulation of Employment Act, 1948, by cls. The term welfare has not been defined but in view of its juxtaposition with other terms, in our opinion, the interpretation of the term should be made ejusdem generis, and, accordingly, cannot be stretched to include educational facilities. Section 3 of the Dock Workers Regulation of Employment Act, 1948, by cls. (g) and (gg), enables the authorities to frame scheme to ensure a greater regularity of employment and for regulating the employment of Dock Workers and also indicates that such scheme may provide, amongst others, for welfare of the officers and other staff of the Board [vide Clause (g)]. A careful consideration of the language indicates that such welfare is not intended to mean and include educational facilities to the children, even of Dock Workers. It is, therefore, clear that the appellant has no liability nor any right to expend for extending educational facilities to the children of Dock workers. The concept of promissory estoppel, therefore, on the face of the aforesaid legal provisions, cannot become applicable as to create any liability or right for the appellant for maintenance of the schools as claimed by the writ petitioners. This view of ours finds adequate support from the authoritative book of Wade when the Author at page 270 records that 'no estoppel can legitimate an action which is ultra vires'. Same is the trend of observation of Spencer, whose book records, "It is a good affirmative answer to a case of estoppel by representation that the allowance of the estoppel must result in an illegality". No writ, therefore, can be issued directing assumption of powers or liabilities, which are ultra vires any person, officer or Corporation by application of the principle of promissory estoppel. In the aforesaid facts and circumstances, the contents of the guide books, 1986 as referred to and relied upon by Mr. Moitra, do not have any binding force. No doubt it has been strongly contended by Mr. Moitra that right to education is a fundamental right and a binding obligation on the State or its instrumentality but no benefit from such submission possibly can be reaped on the basis of the writ application, where the petitioners were not those, who were entitled to the benefit, but those who were teachers of the Schools in questions and were claiming to get monetary enrichment of their own. Mr. Mr. Moitra relied on a decision of the Supreme Court, in the case of Assistant Commissioner of Commercial Taxes vs. Dharmendra. Trading Company, reported in AIR 1988 SC 1247 , in order to sustain his submission that it was not open to an instrumentality of a State, in this case the appellant, to contend that the decision was ultra vires and, therefore, not enforceable. The said case is distinguishable because the Supreme Court ultimately traced the source of power exercised in s. 8A of the Karnataka Sales Tax Act, 1957. Therefore, the said decision is distinguishable on facts. The other case on which Mr. Moitra, relied, in support of his argument that even if the Board had no statutory authority to run the school yet the action having already been taken notwithstanding its ultra vires nature would continue to have its effect in creating a promissory estoppel against the Board till declared to be ultra vires by a competent Court of law, is the case of State of Punjab and Ors. vs. Gurdev Singh, Ashok Kumar reported in AIR 1991 SC 2219. On an analysis of the said case, it appears that a party having proper locus standi can assail the validity of such an act or action and in this case such a challenge has been thrown by the appellants. There cannot be any bar to take a defence to that effect and invite the Court to adjudicate the propriety of such a defence. 7. The last point, which we have to deal with, is the question of legitimate expectation said to have been given rise to by the action of the appellants. Where the action itself is ultra vires the provisions of this statute, which creates the instrumentality which has taken that action, there cannot exist any legitimate expectation or in other words, the expectation of the persons benefited by the same cannot be legitimised. The writ petitioners, who are the teachers of those schools, could not have legitimately expected any liability on the part of the appellants to maintain the school as a measure of welfare and continue to pay their salaries in accordance with the scales prescribed by the Government for the primary teachers. The writ petitioners, who are the teachers of those schools, could not have legitimately expected any liability on the part of the appellants to maintain the school as a measure of welfare and continue to pay their salaries in accordance with the scales prescribed by the Government for the primary teachers. In AIR 1991 SC 2219, due to intervention of the bar of limitation, the Court was not required to decide as to in what manner and by whom the enforcement of an ultra vires order could be resisted and to what extent. 8. For the aforesaid reasons, the writ application must fail and the appeal must succeed. The order of the learned Trial Judge deserves to be and is, accordingly, set aside. There will be no order as to costs. Amitava Lala, J. : 9. I fully agree with the observation in coming to the conclusion by Hon'ble Mr. Samir Kumar Mookherjee, Acting Chief Justice and in addition thereto I say as follows:- We have travelled through various judgments from old time till this date as well as comments of the jurists which are conceptually similar in line, as such, we have not specifically dealt with the same to avoid the prolixity. We have carefully considered judgments reported in AIR 1986 SC 806 (Union of India & Ors. vs. Godfrey Philips India Ltd.) and (1996) 6 SCC 634 UTC Bhadrachalam Paper Boards & Another vs. Mondal Revenue Officer A.P. and others) but we have not found any change of principle within this decade. The Court observes that if it is found that the act done by the Government is invalid and ineffective for non-compliance with the mandatory requirements of law it cannot be held that notwithstanding such non-compliance, it yet constitutes a 'promise' or a 'representation' for the purpose of invoking the Rule of promissory/equitable estoppel, which goes straight against the very basis of the judgment of the Writ Court. 10. Principle of promissory estoppel derives from the illegality or intra vires act of the public body under a statute. As and when statute is silent about the act of the public body, it cannot be said to be discharge of public duties. Therefore the act is nullity. Hence such act should have been declared as ultra vires. No ultra vires act can be implemented because the source is unfounded. As and when statute is silent about the act of the public body, it cannot be said to be discharge of public duties. Therefore the act is nullity. Hence such act should have been declared as ultra vires. No ultra vires act can be implemented because the source is unfounded. It cannot be said to be promissory estoppel applies irrespective of provisional requirements under the statute. In public law the most obvious limitation on the doctrine of estoppel is that it cannot be invoked so as to give an authority powers which it does not in law process. In other words, no estoppel can legitimate action which is ultra vires. Promissory estoppel is an equitable principle and if there is any conflict between law and equity, the law will prevail. 11. Doctrine of legitimate expectation is a foot step towards an equitable relief but derives from the statute. It must be consistent with the operation of the Statutory Rules, Orders or Act. Therefore the expectation depends upon the legitimacy of the act. An illegitimate act cannot, said to be solid expectation as expressed by the learned Judge but a sandy expectation according to us. It cannot give rise to sufficient locus standi for judicial review. Appeal allowed.