I need a single strip of wood planed

I've got a strip of 15mm varnished plywood just over 2m long, 16cm wide, eg quite long and narrow. I need a tiny bit planed off the length edge, the amount to be planed varies - eg c.7mm at the top, down to about 1-2mm at the bottom. (see photos for reference). This is a thin sliver, but i need a good straight line, so my sanding tools are not suitable. It needs to fit into a pre-existing cavity which cannot be re-sized. A strip of masking tape is on the wood as a cutting / planing guide. I just need the tiny edge planed off, retaining the same smooth edge ideally.. Note: this is a small job and better carried out in situ at my property (London Kentish Town area) to ensure a snug fit in its intended location. thank you.