I'd be surprised...
...because single-engine aircraft (manned or otherwise) are banned over the capital. Would require changes to CAA regs. It's why you can't take a Cessna 172 into City Airport and you never, ever see single engine light aircraft over London despite the number of small airfields circling the M25.
There's no way I'd want anything as dangerous as an unmanned, four tonne radio controlled toy with a rotten safety record buzzing around over my home. If this starts to look likely I hope that East End residents (as I belive Lewis is) will write to their MPs. I will.
What's wrong with just putting some actual policemen on the streets and backing them up with a helicopter?