Apologies for all the exclamation marks, but my god! My DS, who has always been one of the world's most appalling sleepers and who typically requires around an hour of patting and lying him back down and hand holding, has just lain down and gone to sleep all by himself for the very first time ever. He was playing around in the cot and not wanting to sleep so I left the room for a little bit. Instead of wailing and screaming "Mummy!" as usual, he chatted to himself for a little while, then gave a big sigh and all went quiet. Utterly confused, I tiptoed back in after 10 minutes, half expecting to find him spirited away by aliens, and he was...just quietly sleeping. 
This has never happened before and will probably never happen again but I just wanted to let you all know. There is hope for every one of us!