According to Monty Don - yes.

I cut all mine back on a regular basis,or they get too leggy..they soon put another good show on ..

some can be cut back to 2 inches tall and will flower again in 2-3 weeks.

Mine get a haircut too, does them the world of good!

I cut the big ones but never thought of cutting sanguinium as it goes on flowering anyway.

thanks everyone, I have cut it back as the roots had got quite large and were pushing a small dry stone wall over, so I had to dig some roots out as well, now I will soon have more plants to pass on to friends,