Squeal from engine bay when ignition turned on

Stringster

Missed gear
Joined
Jan 16, 2006
Messages
389
Reaction score
8
Points
18
Location
Kent
There is a squeal coming from the engine when the ignition is clicked on but the engine not started. Not investigated properly yet, but what is triggered to run when the ignition is clicked on?
Sounds like a belt slipping squeal but perhaps more metallic.
No other problems and running fine.

It's a 2.0 Tfsi.