Pieces of Martinware pottery were stolen from the Pitzhanger Manor House in London in March, days after they appeared on the BBC programme Antiques Roadshow.

Ealing Council, which runs Pitzhanger, said thieves broke into the gallery at about 3am, lifted a window out of the Grade I listed building and made off with 22 items. But the theft was not discovered until the next morning.

A council spokeswoman said: 'The sensor alarms were activated and the council's monitoring contractor attended the scene. The circumstances as to why the theft was not discovered until the following morning is still under investigation.' The Victorian wing where the items were displayed has been closed indefinitely.

Helen Walker, an arts planning manager at Ealing Council, told Museums Journal that the thieves took the most expensive pieces -
estimated to be worth £240,000. A replica was also stolen. She said: 'One would suspect that someone had chosen the pieces to order.'

The Martinware Pottery is stoneware created by the Martin Brothers between the 1870s and the early 1900s. The best-known pieces are bird sculptures and 'grotesque' objects including jugs and vases. The collection was bequeathed to Ealing Council in the 1980s by a local couple.

The 22 items make up 5 per cent of the total Martinware collection - some of which is in store. Scotland Yard is 'in full swing' with the case, said Walker.

The council will now undertake a security review. Walker said any alterations that might be needed to a listed building could take some time. But she said: 'I don't believe much else could have been done to avoid this happening.'

Felicity Heywood