Some vignettes from today that describe it overall:

This morning James came into our bed, he was happy and smiling. He lay there babbling unintelligible stuff, and I ‘babbled’ back (hello James, hello, wheres your nose? etc).
After a little more of his babbling he went quite I looked over and he had a look on his face like he was about to cry. Why? no idea! So I cuddled him and he grabbed onto me.

No bread in the house so gave him two weetbix for breakfast, he was not that happy but ate about half. Then I made pancakes for the house inhabitants which included Holly, James had some but spat it all out.
Once Holly had been picked up we went to go swimming but it being Anzac day the pool was shut, went via the tip and dropped off waste oil and various broken appliances that I had put in the back of the car. To Grandmas house and James played a bit with the toy matchbox cars, well when you say ‘played’ I mean looked at and held in his hands.
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So what has James done today and what have I tried:

I have tried getting him to play with various things. He has been most content to come down into the garage and hop into our (new) car, muck around inside, get out, go up the stairs. Come back down, look at the car. Play with the Ford badge (pivots to expose the bonnet release).
I have tried really hard talking to him. Getting down low face to face, being patient. There's been basically no language today at all.

I have read books, he hardly looks, he’s barely ‘there’ at all. We have got puzzles from the toy library he is not interested. We got some giant block things you fit together and can make shapes, he’s not interested in those except marginally initially, meanwhile Hannah (and Holly) did not stopped playing with them, making ‘trains’ and dance mat, boxes to get into, fences, houses etc etc.
He’s not interested in TV.

He has been on his bike around the house, he is enjoying his bike but he never looks thrilled, it's like it's something he does to while the time.

What has interested him:
Playing in the car, pushing buttons etc.
I took him on the tramp, he does like this but only for so long. I took him to the park for a swing, he does like this quite a lot; some things never change.
I put him in the Spa, he does like this but he was only in there a wee while he got out grizzling.
He does honestly like having cuddles with me, and whenever I have sat down with him we have had a cuddle. He’s quite content to lie on me and have his head stroked for a bit.
The buckle on his car seat has always intrigued him. He still plays with and tries to open this.
The chain release thing on the safety chain on the baby swings at the playground. Can’ do it but loves it.
Wee George came around, but James didn’t even so much as look at him. George just looks at James occasionally with the puzzled look and doesn’t bother.
Also yesterday at the park a little boy from James’ little school came up and said ‘Hi James’, James didn’t even smile or acknowledge him. Yet we know James likes going to little school.

Put him to bed early, he was grizzling lots since before tea, I felt he was tired and he was asleep before 7pm, so maybe that was a lot of the problem.