Conmen pretended they wanted to buy an elderly man's £1m townhouse before moving in and turning it into a squat.

Police said the gang tricked their way into the four-storey Victorian terrace in Jericho after spotting a for-sale board outside and persuaded the owner to let them have a look around.

The pensioner is then thought to have asked them to post the keys back through the letter box of his nearby home when they had finished looking at the five-bedroom house.

But police believe the gang refused to leave the house in Walton Street - turning it into a squat and using it as a drugs den.

About 17 police officers and police community support officers raided the house yesterday.

After smashing down the door at about 5pm they seized drugs paraphernalia including a cannabis grinder and a homemade pipe.

They also seized about seven bicycles and about 80kg of lead - both of which officers believe were stolen.

Four men were arrested on suspicion of theft and handling stolen goods.

Pc Leigh Thompson, the county's drugs coordinator, said: "We executed a search warrant because we had information that someone was dealing class A drugs from the premises and we had numerous complaints from the local residents that drug dealing and antisocial behaviour were taking place.

"We don't want this sort of thing in our city.

"It had been on the market - the For Sale sign was outside. Some chaps came round and the owner said Let me show you around'.

"He opened the door to them and gave them the keys and said When you have finished drop them back through the door' - and they have never dropped them back."

Pc Thompson said the owner of the house was extremely upset about what had happened and would be now be supported by mental health experts.

He added he believed the gang moved in about four weeks ago and said the house would now be temporarily boarded up.

A drug case officer from Oxford City Council's Crime and Nuisance Action Team (Canact) also attended the raid.

Neighbours living near the house said they didn't realise the property was being used as a suspected squat.

But one man, who asked not to be named, said: "I am not shocked in the slightest. I knew it was for sale and I thought it had been sold."

Another neighbour added: "It was quite quiet until the police came around. We just heard them knocking the door down.

"It was going to be sold for £1m. It was inhabited by students and then it was empty and then these people came in.