英国过境签证求助！

想从英国转机去欧洲其它国家，想申请一个过境签证，48小时内的那种；

查了一下官方说明是这么说的：


Visitor In Transit (VIT)

Visa nationals whose ticketing requires them to change airports in the UK and where the connecting flight is less than 48hrs between arrival and departure should select this visa.


Contrary to its title "visitor in transit" you may NOT visit the UK, this visa is solely for the purpose of changing airports i.e. London Heathrow to London Gatwick. Sightseeing, shopping, visiting friends and/or family is prohibited.


但是我想利用这48小时去伦敦见见我的朋友，按上面所说的是不行的；但如果我过了边防，当局如何控制让我不能Sightseeing, shopping, visiting friends and/or family呢？哪位达人知道？谢谢！