Stop tap/cock

[Kmurphy]

I don't appear to have an internal one... bit worrying. I've been told it's illegal, anyone confirm that?

Anyway... I have an external one and a long key... but I also found the pictured. Can anyone tell me if it's a stop cock or not or what it is... and what might happen if I turn it with a plumbers key, quite tempting that...

It looks like a stop cock without a key, but also has a little outlet underneath (I think)

 

[JohnD]

It is a drain cock. I have no way of knowing if it drains the radiators or one of the water pipes, or an outdoor tap.

It is not illegal to lack an internal stopcock, but it is inconvenient. Verify that you can operate your outdoor one, and ask around for a recommended and experienced local plumber.