Thieves have stolen a series of important architectural artefacts worth more than £250,000 from the Grade II*-listed Old Conduit House in Hampstead.
The robbers broke into the 19th-century building - designed by John Burlison, an assistant to George Gilbert Scott - and stole stained-glass windows, marble pillars, fireplaces and banisters.
The building is currently being redeveloped and the theft took place when there was no security presence. Police believe the thieves entered via scaffolding erected as part of the construction work.
'Old Conduit House is an important building, on the buildings at risk register, ' an English Heritage spokeswoman said. 'The Gothic-style house has a fine interior and we are saddened to hear of the recent extensive damage.
'Theft from listed buildings is an ongoing problem, particularly when the buildings are vacant for some time. Such thefts are highly specialised and represent a lucrative business, and we welcome attempts by Camden council and the Metropolitan Police to recover the stolen items, ' she added.