Southwark is one of the worst areas for feral young males on mopeds stealing phones, in particular round Surrey Quays in Rotherhithe. Police have been putting up signs round Southwark warning people of moped thefts, and by bus stops too.
I think we should all be aware of them and avoid walking down the pavement with a mobile and ideally, walk along the pavement in the other direction, the opposite of where they are going. Of course, in pedestrianised areas, just be vigilant. These men are particularly looking for those who are easy targets, and not paying any attention.
I don’t have an expensive iPhone and my phone is also registered on immobilise.com and is password-protected after a few seconds.
I have only noticed signs going up in the last a couple of years, so may be this is a new phenomenen learned from abroad.