Happy New Year etc.
Brexit, Daesh, Trump etc, blah blah, but more importantly my boiler is
having issues.

No hot water this morning and it was evident that the boiler (a 30 year
old Potterton) was off.
It restarted OK and ran for a few minutes.

I changed the thermocouple but it behaves the same.
In fact, if it's just the pilot that is on, then it stays on. It's only
when the burners start that it shuts down after about 2-3 minutes.

Any ideas or is it time to call a man in?
Ta.