( 1 ) - The respondent Nos. 1 to 4 in this appeal are assignees of a lease-hold interest is respect of a plot of land measuring 3 cottahs 13 chittacks and 31 square feet, being plot No. 7 of Calcutta Improvement Scheme No. LXIV.

( 2 ) THE lease in respect of the aforesaid plot was initially granted by the Trustees for the improvement of Calcutta in favour of one Ajit Kumar Hazra, Dwijendra Nath Hazra and Amar Nath Hazra on 18th June, 1962 for a period of 99 years with option of renewal for a further period of 99 years on various terms and conditions.

( 3 ) ONE of the covenants made by the Lessees and to be performed by them is as follows:"6. Not to assign or transfer in any way or to mortgage the said land without the previous consent in writing of the Chairman of the board. "

( 4 ) THE lessor on its part made several covenants to be performed by it, including the following :"2. that the board will on the written request of the lessee made three months before the expiration of the term hereby created and if there shall not at the time of such request be any existing breach of non-observance of any of the convenience on the Lessee grant to him a lease of the said lan