She often stayed at Brown's Hotel in London, & it's said that it inspired her mystery novel "At Bertram's Hotel"
[DOC] [TLE] Agatha Christie tourism: From North Yorkshire to the Middle East ... [PAR] Sep 11, 2015 ... At the top end of the price spectrum there's Brown's Hotel (020 7493 6020; ... 
here, and used it as the inspiration for her dubious, late-period Marple thriller, At 
Bertram's Hotel.