The City of Westminster has some of the most expensive homes in the world, so it is surprising that some residents are able to rent luxury properties and claim housing benefits.

Inside Out's Mark Jordan joins Westminster Council's fraud inspectors in a raid on one of hundreds of illegal sub-lets.

The cost to the taxpayer from these fraudulent claims is estimated to be around £10m in lost revenue.

Westminster Council's anti-fraud tsar, Councillor Lindsey Hall, talks about the challenges of tackling the problem and dealing with what she describes as "outrageous" cases.

Inside Out is broadcast on Monday, 30 September on BBC One London at 19:30 BST and nationwide thereafter on the iPlayer.