There is a 2-4-1 on some of Gordon Ramsey's restaurant for the set menu:
London House (2 courses £20 / 3 courses £24)
Maze Grill Royal Hospital Rd (£24/£28)
The Narrow (£20/£24)
Heddon Street Kitchen (£24/£28)
Maze grill Park Walk (£24/£28)
Union street Cafe (£24/£28)
York and Albany (£20/£24)
Maze Grill Mayfair (£20/£24)
Fortunately or unfortunately they are all based in London and set to expire 9 February 17.
They say you need to book first but I called outside and went straight in which they were fine with.
I might add that with drinks, some sides and service we ended up paying c£35 per head but the food was brilliant.