Removing aerial from the roof

Wondering what’s the best way to removing the aerial on an S1 Exige - can’t seem to get a spanner from the hinge side as the nut is higher up out of sight, and it seems fairly well set back from the front (roof vent) side.

Anybody done it recently?

Ok so the plan was to remove the aerial base to change the gasket. However, I managed to get a new gasket from Simon Scott-Russell, which doesn’t go under the base unlike the original one. So I could cut-off the old one and just slip the new one over without removing the base - literally took 1 min.

Might save someone a bit of pain in future!