Stick an Alan in there G
And give it a good whack with a big 'ammer
Shock it loose!!
constant pressure will strip it..
funny enough I thought of using my cordless drill , set onto hammer with the clutch set low so it slips and on reverse so hopefully the vibration will help loosen it , always worries me hitting aluminium too hard
but think a few gentle taps first certainly won’t hurt , got some small tools to go into the dremel as I want to clean it all up first , particularly round the edges, also got some small wire brush attachments for it
useto have great success with boilers removing old plugs using the cordless drill set on hammer