Just to make sure i am not deluding myself 
Letter from school said his BMI is 18.9 which puts him on the 98th centile and they will review in 6 months.
He was 5 in July and is 113cm tall and 24.2kg.
He is very very active - doesn't stop moving all day. Very athletic - been riding a bike since he was 2, swimming independently since he was 3. Spends most of his free time riding his bike or kicking a football around.
Photo looks like he is pulling his tummy in, he wasn't, but he was stretching up to throw something.