Pressure too high on Potterton Titanium Boiler

Last night I noticed the Boiler on E1. After a few times in the past having this issue and being advised on how to re-pressure the boiler, I pressured it to just under 2 - Boiler working again!

This morning I came down to find out the under floor heating hadn't heated up the kitchen as much it normally did and checked the boiler.
The pressure needle was in red (over 3!).

I immediately switched off the boiler and have left it since. Not sure what I have done wrong?
The boiler filling knob is off and looks all ok to me.
It has been around 20mins since switching off and its now in the middle of 2 (green).

Any ideas what may be wrong and how to resolve this?
Do I need a Gas Safe engineer out or can I resolve myself?

Picture one it looks like you have left the fill valve off it should be across the pipe not in line

After ensuring fill line is isolated watch the pressure when you fire up the boiler, 2 bar (cool/cold) may be too high and increase and lift the PRV at 3 bar, normal cold fill should not be > 1.5 bar.