To the extent that Italy held the territory by UN mandate, the trusteeship provisions gave the Somalis the opportunity to gain experience in political education and self-government. These were advantages that British Somaliland, which was to be incorporated into the new Somali state, did not have. Although in the 1950s British colonial officials attempted, through various administrative development efforts, to make up for past neglect, the protectorate stagnated. The disparity between the two territories in economic development and political experience would cause serious difficulties when it came time to integrate the two parts. Meanwhile, in 1948, under pressure from their World War II allies and to the dismay of the Somalis, the British "returned" the Haud (an important Somali grazing area that was presumably 'protected' by British treaties with the Somalis in 1884 and 1886) and the Ogaden to Ethiopia, based on a treaty they signed in 1897 in which the British ceded Somali territory to the Ethiopian Emperor Menelik in exchange for his help against plundering by Somali clans. Britain included the proviso that the Somali nomads would retain their autonomy, but Ethiopia immediately claimed sovereignty over them. This prompted an unsuccessful bid by Britain in 1956 to buy back the Somali lands it had turned over. Britain also granted administration of the almost exclusively Somali-inhabited Northern Frontier District (NFD) to Kenyan nationalists despite an informal plebiscite demonstrating the overwhelming desire of the region's population to join the newly formed Somali Republic.

Answer this question, if possible (if impossible, reply "unanswerable"): In what year did Britain try to purchase Somali lands from Ethiopia?
1956