We're trying out a trick to make Elijah feel more secure in the cot by putting rolled up bassinette blankets and muslin wraps around him, underneath the fitted sheet. It's had some success.
Elijah managed to not get out from under the covers at least, sleeping through until 6:30am. He had a great nap this morning (about 90 minutes) and then a so-so nap of about 25 mins at lunchtime. I tried putting him down in the afternoon, but it was over an hour of alternating between crying and fussing in the cot with me soothing him, me rocking him and him deciding it was play time again. I eventually gave up and got him up for a feed.
So we're not really sure what is the verdict on this new trick at the moment, but we'll give it another day or so before I try another tactic.