From

https://www.gov.uk/displaying-number-plates/rules-number-plates

"
If you ride a motorbike or motor tricycle

Motorcycles and motor tricycles registered on or after 1 September 2001 must only display a number plate at the rear of the vehicle.


If you ride a motorbike or motor tricycle registered before 1 September 2001 you can also display a number plate at the front, but you don’t have to.

Motorcycle and motor tricycle number plate numbers should be on 2 lines.

"
I took mine off when I collected it and haven't been stopped