Big slot in the cap and I'm having trouble finding a metal bar thin enough to drop into the slot but strong enough not to bend when trying to remove the cap. There must be a simple way to get that cap loose without damaging it with a cold chisel or other tool.
Any ideas before I go and bugger it up?

Drag link socket. May have to grind it a bit depending on what you find.

You can usually find them at a flaps if you don’t want to wait for an online order

Thanks. Didn't know these even existed!

Impact driver with a large flat head bit

Always been my go to tool and always worked. For clarification, I use a hand impact driver.