This was my big project over the whole summer. I started with McCall's 2252 pattern and did a lot of toiling and fitting. I changed the pattern quite a lot to create the trench coat of my dreams. I have documented the whole process on my blog.
How to use tie interfacing to gather the sleeve heads...
I used Nikwax Cotton proof to make my coat water repellant.
Piping around a corner. Clipping is necessary.