Number 1 Millbank, the former headquarters of the Church Commissioners for England, will be converted into much-needed administrative space for the peers who are apparently crammed nine to a room at present.
Designed by William Caroe, the 1904 red-brick building was fully refurbished just five years ago and, in a strange quirk of fate, Caroe's grandson is now one of the staff at PMT charged with masterminding the latest overhaul.
The London-based conservation specialist was chosen ahead of 35 other practices that initially submitted an expression of interest in the job.
The first proposals from PMT about how it intends to find room for all the lords, as well as their burgeoning back-room staff, are expected to be unveiled early next year.
One of the key design drivers which PMT will have to take in to account will be how to provide easy access to the Houses of Parliament. The division bell, which summons peers to vote in the Palace of Westminster, gives them just six minutes' warning.
Cliff Cowell, an architect with the Parliamentary Works Services Directorate, which is overseeing the refurbishment, said: 'This is an opportunity to equip the House of Lords for the future.
'We are embarking on an adventurous journey and all augurs well. We know what we want; we have the people we want; we have set course; and now we are just waiting for the right wind.'