This old snapshot — it measures about 2½ inches by 3½ inches — has the following written on the back:
after bombing of London
Indeed, according to a 2011 history piece by The Telegraph, "In 1941, Christie's headquarters suffered a direct hit during the Blitz and moved to Derby House, near Oxford Street, only returning to King Street in 1953."
British History Online adds a further bit of detail about the bombing and rebuilding at No. 8 King Street:
"Christie's premises were destroyed by incendiary bombs on the night of 16–17 April 1941. The firm moved to temporary quarters at No. 16a St. James's Street and later to Spencer House. When the King Street premises were rebuilt in 1952–3 the main façade of the old building, which had escaped destruction, was retained and reconstructed as part of the new work. No. 5 Bury Street was rebuilt in 1954–5 and Nos. 47–48 Duke Street in 1956–7."