Thanks again for your reply!
So this is what happened this morning….grateful for any thoughts.
He woke at 6.30. Normally I would wind down at 7.30 and have him in the cot by 7.45 latest. He then plays for 10 mins and goes to sleep for 45 mins.
Today I did wind down at 7.40 and he was in the cot 7.55. I saw his usual tired signs after an hour but they had passed but the time he went down.
He cried within 2 mins of me leaving the room. I went back and forth a few times - when I went in he started grinning and chatting, but cried when I left. Eventually I resorted to picking him up and rocking him. Between 8.15 - 8.45 I rocked him to sleep 3 times - but every time I put him down his eyes flew open. I eventually abandoned the nap at 8.45.
We played quietly for 15 minutes and then at 9 he seemed sleepy so i tried again. This time I just rocked him to sleep from the start which I normally don't do, and he fell asleep after 10 mins. I put him down at 9.15 and he woke up crying 30 minutes later. i tried unsuccessfully to extend the nap.
So keeping him up an extra 10 mins meant:
He didn't settle himself
He wouldn't settle with me
Having to retry for the nap later and settle by rocking.
Sleeping for 30 mins instead of 45.
I just don't understand him - his 45 minute nap must be due to being under tired but 10 mins extra and he is so overtired he won't nap at all?
Do I persist with keeping him up longer? Or is it possible he really does have a very short first wake time?