The 600-bedroom hotel, providing state-of-the-art business facilities, is to be directly linked to the terminal.
BAA expects construction will start in September 2005, with completion in early 2008 to coincide with the opening of the terminal.
Jonathan Manser said that the hotel is to be part of the T5 family of buildings and a destination in its own right. He added: "It will need architectural integrity to succeed as both. This is an exciting challenge and we cannot wait to get started."
BAA Lynton managing director John O'Halloran said that Manser had been appointed after a competition in which five hotel architects took part.
O'Halloran added: "Manser was the clear winner of this competition in terms of its ideas, commitment and understanding of the brief."
He said that BAA would be going to the market in the new year to secure an operator for the hotel.
BAA Lynton is the commercial property division of BAA and established its Airport Hotels Partnership in March 2000. Initially, the partnership had an investment fund of £200m, managed by BAA Lynton, and comprised eight hotels.
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