Plant identity and advice please
Can someone pleasr identify this plant for me. I've had it in my garden since we moved here 2 years ago. I have cut it back after flowering and it has grown back and consequently assume I am doing right by pruning. Not entirely sure when it should be pruned and by how much. Any advice much appreciated.
In the sticks near Peterborough
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.