Legalising prostitution
Here in Germany, prostitution is legalised but under a number of constraints. These include that prostitutes may only work in licensed brothels, brothels may only be located in discrete locations, prostitutes must be regularly checked by a doctor, etc. As they are not demonised by the law, prostitutes can call on the police if they are assaulted and are not easily controlled by gangsters. Prostitutes have their own union, have health insurance and pension schemes.
Of course, gangsters then traffic women from abroad as they are easier to control due to their illegal status but punters don't need to risk going to these people as they can visit a legal brothel. Legalistion removes trade from the gangsters - so they are better off in Britain where everything is illegal and therefore, easier for the gangsters to control.
The other problem in the UK is that, despite assurances to the contrary, many foreign prostitutes who were trafficked are deported right back to their home countries and into the hands of the gangs who trafficked them in the first place.
Whilst the situation in Germany is probably not ideal, it is much better then that in the UK and I can only think that the the new UK legislation will make things worse.