A young man was so fascinated by a rainbow that was created under the sprinklers of a water truck that he failed to notice cops on his tail who later fined him for riding without a helmet.

The man, who was not named, was joined by a friend as the two followed after the truck along the streets of Changzhou, in China's eastern Jiangsu Province.

Both were captivated by the sight of a stunning little rainbow forming beneath the light spray of water from the truck's sprinklers.

The rainbow persisted as the truck moved forwards, cleaning the streets, and the two men rode behind it on their motorbikes, wanting to film the scene.

But as they were admiring the colourful arch, they apparently did not notice there was traffic police standing further ahead and were promptly stopped for not wearing helmets.

They wound up getting fined, with a short cutaway at the end of the video showing them receiving the tickets.

The man said: 'Because my friend and I were caught for the first time, each of us was fined CNY 20 [GBP 2.25].

'The total cost of the video was 40 Yuan [GBP 4.5]. But seeing the rainbow was worth it. I Hope all people riding e-bikes remember to wear helmets. Safety is the most important.'