How to remove conservatory trim

[Ben Blaukopf]

shows the inside of my conservatory at gutter level. I suspect that there is a lighting cable I need to get at behind the pictured trim. I've tried pulling hard and can't shift nail (?), nor can I get a knife blade under the head in case it's actually a push on cap over a screw.

Any suggestions? Pull harder?

[Ben Blaukopf]

Prised a bit more. It's a cap over a screw. Caused a bit of damage, but no one will ever see it.

[Ben Blaukopf]

Sadly no cable though.

Bit of timber I can't remove behind, and plywood I can't remove (because the timber is sitting on it). Damn.

[SteveW]

It happened to be a cap over a screw, but others should not assume that in the same situation. I have some trim held in place with nails that have a plastic, non-removable cover on the nail head.