Duplicate thread by Prospero
have everything except the last two unclued ... if I'm right that 20's last 3 become 15 down's first, and 16's last 3 become 17's first, so the last 3 of 17 become 20's first, I have a clash because the 2nd letter of 20 must be an A, while the 5th of 17 must be an O ...