Lancaster House, the scene of today's crucial Northern Ireland talks and once described as "the grandest aristocratic town house of the 19th century", has been the opulent setting for many key events which have changed the course of history.
It was there, in 1961, that the decision was taken to kick apartheid-ridden South Africa out of the Commonwealth. And it was in its chandeliered conference room that the historic signing took place in December 1979 which effectively ended the rebellion in Rhodesia and led to the creation of the new state of Zimbabwe.
Lancaster House is a brooding, stone building on the edge of the Mall. Commissioned by the Duke of York, brother of George IV, it was completed at enormous expense after his death in 1827 by the Marquess of Stafford, later Duke of Sutherland.
Until this century it was known as Stafford House. The change of name happened after 1912 when Sir William Lever, later to become the first Viscount Leverhulme, bought the remainder of the lease, renamed the building after his native county, and presented the lease to the nation to provide a new home for the London Museum and a centre for government hospitality.
Lancaster House is regarded as the finest example of the then-fashionable Louis XIV interiors in London. Indeed, so lavish was the building that Queen Victoria once, on visiting the second Duchess of Sutherland from nearby Buckingham Palace, observed: "My dear, I have come from my house to your palace."
The Great Staircase Hall is the most splendid of its kind and date in England. Adjoining it is the State Dining Room, with five tall windows looking across the garden to the Mall.
The state rooms on the first floor have been the scene of many historic events over the centuries. Lord Shaftesbury here advocated the reforms which led to the Factory Act, and Charles Sumner and William Lloyd Garrison pleaded for the abolition of slavery.
Some historians and architectural experts have lamented some of the recent "restoration" work. One of them complained about the "neon lighting in the cornices, white gloss everywhere and hideous red carpets".
But it nevertheless remains one of the most splendid and lavish examples in Britain of the opulent interiors of its time.