How to unwarp an antique wardrobe door?

[Userwoteva]

I have a Georgian pine knock-down wardrobe. The locking door (which closes on top of the other door) has warped outwards by 1cm at the top centre edge. How can I get it to flatten out? What it needs is something on the outside pushing it forwards but that would mean having some kind of surface mounted bolt which would be unsightly. It can't be pulled in from the inside by way of a bolt as this door closes over the other one. If I take the door off and pile a million books on it flat on the floor will that do the trick? & how long do you think it would take? Last time I tried to flatten wood it was engineered oak planks that had banana'd & they refused to oblige!

Show us a picture of it, front and back.

I've put a panel-pin in the door top edge & secured it closed with a skinny black ribbon tied to the internal bolt of the left hand door. Forgot to take a reverse view pic but it's exactly the same, three panels visible, no other wood/thickness involved.

the gap

OK, it appears to be of panelled, M&T construction, and I think I can see dowels in the tenons.

Take it off its hinges

Stand it on some books, one at each corner. The "warped" corner, put it with the warp upwards, and have fewer books under it, by about twice the amount of the warp.

Stand on it so that all four corners press onto the books. There should be a loud cracking noise as the joints move to a new position. When you get off, it might be more or less flat. If not, add or subtract books from that one corner and do it again.

If it was me I would stand against it and pull it by hand, but that is harder to describe.

You could do it in a more wimpy way with blocks and a Spanish windlass if you had the equipment.

p.s.
I think I can see something through the gap. What is it?

Piglet it looks like the inner edge of the door.