Officers then handed out a fixed penalty notice but refused to tell them how much the fine would cost, simply saying they would receive it in the post.
A dozen or so officers then began hauling away the boxes of balloons to the council’s municipal office at the edge of Wembley Park.
A council spokesperson confirmed action was taken against Mr Wilsher and added balloons can present a “serious safety risk” when in large quantities.
Mr Wilsher said he felt intimidated by the officers as they were dressed in black and were recording them.
He said: “My son was quite upset by the whole thing, it did feel very heavy-handed and overzealous.
“Rupert was hugging into his nana. He was quite shell-shocked by it all, he had a cry about it later when he had compartmentalised it.
“We were just trying to bring some colour, noise and spectacle to the day but that was taken away from us.
“I will absolutely be appealing the fine, I will be gunning for them. Pragmatism, common sense and manners, not overzealous officials, will win out.”