Bleeding a Roca Radiator

How did you get the valver to let out air? I have a problem with two radiators that I had to remove for decorating and even though I have taken the cap off the radiator bleed valve no air seems to escape. The bottom of the radiator is warm so I have circulation at least. Does any body have any ideas as to what is resrticting the valve?
 

The bleed valve is top right of the radiator.  Long time since I did it but I seem to remember it's a screwdriver you need.  Might be an Allen key.  Just loosen it and air will come out.

The best way to get the air out of your system is to bleed to towel rail in the bathroom as it is the highest point on the system. All you need is a flat bladed screwdriver to turn the small screw at the top of the valve on to of the rad. Run the system for a few days after, then bleed it again. When the system is cold remember to top it up with water to the 1.5 bar mark on your water guage