I was delighted to have a good phone chat with the Mendelssohn scholar R. Larry Todd the other day about his reconstruction and completion - using the finale of the Violin Concerto - of Mendelssohn's Piano Concerto No.3 in E minor.
The full text is viewable over at my BBC Radio 3 Mendelssohn anniversary blog (which you and I know is really called Felixcitations). From there you have to click through to another page to read it because apparently it was too long for a blog.
Meanwhile you can hear the inimitable Stephen Hough playing the better-known PC No.1 at the RFH tonight.