Grand Reception Room Early diplomatic entertainment by the Foreign Secretary took place in local taverns or at his home but, by the 1850s, the London Diplomatic Corps had increased so greatly that there were very few noblemen's houses which had rooms sufficiently large to contain it. Furthermore, diplomatic business was broadening in scope as well as in size and the Office needed conference accommodation. The London Conference of 1831 on Belgium, for instance, had taken place at the old Foreign Office, but the Secretary of State had had to vacate his room for the duration, as it was the only one big enough for the delegates. In 1858 therefore, the Parliamentary Committee on Foreign Office Reconstruction was told by Edmund Hammond, the Permanent Under Secretary, that in any new building, it was 'essential that the Secretary of State for Foreign Affairs should have the means of giving large dinners...and that he should have reception rooms capable of holding 1,200 or 1,500 people'.

Following these representations, the architect of the new Foreign Office, George Gilbert Scott, designed a magnificent suite of three rooms on the first floor. This consisted of the lofty 'Cabinet Room', (now known as the Grand Reception Room) with its barrel-vaulted roof and windows looking out on to the Main Quadrangle and the Foreign Office courtyard, the smaller square Dining Room, and the Conference Room with its gilded ceiling supported by brackets embellished with emblems of foreign countries. The suite was approached by the left-hand branch of the Grand Staircase, with the right-hand branch leading to the Secretary of State's Room. Scott's intention was to create a feeling of grandeur evoked by spaciousness: in effect 'a kind of national palace, or drawing-room for the nation'.

Until 1914, the suite was in constant use for entertainment and conferences. It was invariably the venue for the royal Birthday celebrations, 'when the great double staircase, with the guests ascending and filling the open corridors above, provided one of the most magnificent sights in London'. It should be remembered, however, that identification of individual rooms in the suite is not a straightforward matter, as each has been given various names over the years. The Dining Room, for example, was sometimes also known as the Cabinet or the Smaller Conference Room, and was, in addition, often used by Lord Salisbury as his office, in preference to the Secretary of State's Room. The Conference Room has also been described as the Dining Room or the Larger Conference Room.

During the First World War, however, an acute shortage of space within the Foreign Office led to the entire Reception Suite being used as offices. This was not a success. The original Victorian decorations had become very shabby, and the rooms were considered too dark and draughty for daily use. When Austen Chamberlain became Foreign Secretary in 1924, he was anxious that they should revert to their original purpose, but the Office of Works asked whether the rooms should be redecorated, and if so, in what style. It was impossible to clean the original stencilling, and it would need either to be repainted or removed. Before any decision was made, however, Austen Chamberlain's attention was diverted towards the negotiation of the Locarno Treaties.

When the Treaties were initialled at Locarno in Switzerland in October 1925, the delegates agreed to come to London for the formal signing of the Treaty in December that same year. The only possible venue for the ceremony was Scott's Reception Suite, so the largest of the three rooms, and the smaller square chamber adjacent to it, were cleared of their former occupants, and the walls were adorned with royal portraits and with one of Lord Castlereagh. The room in which the Locarno Treaties were signed was known in 1925 as the Reception Room, although the Gaumont Film Company's newsreel showing the ceremony described it as the 'Gold Room'.

Later in December 1925, the newly created Royal Fine Art Commission recommended that the original Victorian stencilling should be removed from the walls of the two largest rooms in favour of redecoration in shades of parchment colour, and that the furniture should be upholstered in black and gold silk damask, with curtains of the same material. This fabric, entitled 'Locarno', was designed for the Suite by Charles Ebel, and specially woven by Warner Fabrics. The walls of the small square room were covered in crimson silk stretched on battens, and were hung with portraits of famous Foreign Secretaries. Following this transformation, the three rooms were renamed the 'Locarno Suite', as a memorial to a supposed diplomatic triumph promising an era of international cooperation.

In 1935 the Locarno Suite was chosen for the opening session of the International Naval Conference, and during the State Visit of President Lebrun of France in March 1939, a splendid dinner party in the presence of King George VI and Queen Elizabeth took place there, prior to a theatrical entertainment staged in Durbar Court. On the outbreak of war later that year, the chandeliers were shrouded and the Locarno Suite became the home of the cyphering branch of Communications Department, for whom no other accommodation was available. An even more acute shortage of office space after 1945 led to the division of these rooms into cubicles under false ceilings, and in these makeshift plasterboard hutches, the Legal Advisers and others worked.

This is how the Locarno rooms remained until the FCO's rolling restoration and refurbishment programme reached the Suite in the late 1980s. The plasterboard shroud was stripped from the second largest room of the Suite to reveal once more the coffered ceiling, pilasters crowned with Corinthian capitals, and quadrants supporting gilded iron beams. Circular majolica plaques bearing the national coats of arms or emblems of twenty countries further ornament these quadrants, and the original stencilled design has been reinstated on the walls. The Locarno Conference Room reverted to its original purpose in summer 1990, while the restoration of the Reception and Dining Rooms proceeded between 1990 and June 1992.

In the Dining Room, the removal of the plasterboard and the very dirty red silk hangings uncovered the original stencilled decoration in olive and gold, with red and gold borders. Although faded and damaged, its survival ensured that an exact copy could be superimposed on the walls, restoring the room's authentic Victorian splendour. Two new doors, matching exactly Scott's originals, give direct access into the adjacent former India Office. The restoration of the Grand Reception Room involved much painstaking detective work. The great barrel-vaulted ceiling of the Reception Room was known to have borne an elaborately detailed design of classical figures and signs of the zodiac, but it was feared that the decorators in the 1920s had removed from it with pumice stone every scrap of colour and gilding. Close examination nevertheless revealed that one section had simply been painted over, and scientific analysis of the remains below enabled the ceiling to be reinstated according to Clayton and Bell's original design. The marble fireplaces throughout the Suite, like those in the Secretary of State's Room, date from the eighteenth century and may have been transferred from the old Foreign Office.

Following the restoration, the entire Locarno Suite is once more available for conferences and ministerial and government functions.