He can't have it back now...

I've been having another rummage in my husband's wardrobe and one of his shirts has been transformed into this

This is how it started off

First I removed the collar and the sleeves.  The back had two pleats which made it very full, so I unpicked the yoke from the sides, pulled the pleats out flat, then restitched the yoke.  To make a new collar I folded the shirt in half and drew round the neckline onto paper then drew a Peter Pan collar shape.  I cut two pieces on the fold from the bottom of the sleeves and one piece in interfacing.  After ironing the interfacing to the back of one piece, I pinned the collar rights sides together and sewed round the outer edge.  I then clipped into the curved seam and turned it rights sides out

It took me quite a while to decide which was the best way to attach the collar.     
In the end I machined it to the inside of the shirt then turned the bottom edge of the other side up and slip stitched it in place

To get the right width on the shoulders and sides I laid one of my blouses on top, cut round it, then sewed up the side seams.  I cut what was left of the sleeves shorter and gathered the bottoms into a band and gathered the top to fit in the sleeve hole.  I put a couple of darts in the back to shape the waist and shortened the bottom.
I wasn't keen on the original white buttons because they were really thick (more than twice as thick as a normal button) so I changed them to some navy ones out of my button box.  Because I'd removed the top button when I took the collar off, I had to make a new buttonhole at the top.

It took me a lot longer than I thought it would, but most of that was just thinking about what I was going to do and daring to start!