( 1 ) THE petitioners in these writ petitions under Article 226 of the Constitution have prayed for a mandamus against the Delhi Development Authority (for short D. D. A.) :

1. for restraining the D. D. A. from recovering the ground rent for the plot taken on perpetual lease from the D. D. A. for construction of cinema houses ; and 2. to direct the D. D. A. to carry out and complete the development of civic complex around their cinema houses in ac- cordance with the assurances given to them by the D. D. A. ;writ Petitions Nos. 443 of 1975 and 1041 of 1976 are filed on behalf of the Milan, Cinema at Karampura, Delhi. Writ Petition No. 348 of 1973 is filed on behalf of Deep Cinema at Wazirpur, New Delhi, Writ petition No. 1177 of 1973 is filed on behalf of Payal Cinema Narayana, New Delhi. In support of their claim, the petitioners have relied on the principles of promissory estoppel.

( 2 ) SINCE most of the factual averments and the reliefs claimed are common to all the four writ petitions, we will examine in detail one writ petition, namely, C. W. Petition No. 443 of 1975 as a representative petition.

( 3 ) A plet of land measuring about 2972. 41 Sq. Mts. situate at Sh