Couple of small flathead screwdrivers to lever an end out of its recess and then work round it should work - at least that's what I've used with other circlips.
The occasional Bad Swear may help too, especially when supplemented with a sharp intake of breath.
I've done the swearing, for sure ... the problem is that it's so difficult to get anything in there, and get an angle on it. Would've been a better engineering decision to put some eyes on the thing. First time I've had to had to say a bad thing about Campag design.
Couple of small flathead screwdrivers to lever an end out of its recess and then work round it should work - at least that's what I've used with other circlips.
The occasional Bad Swear may help too, especially when supplemented with a sharp intake of breath.