Is it Illegal to smoke whilst riding a motorcycle?

[Frog_biker]

I can find no specific Law / Regulation that forbids smoking while riding a motorcycle. Certain opinions state that 'you could get ash in your eyes/you could cause an accident' at which point it becomes a contributing factor. There is also the other school of thought which says, you'll have to remove your hand from the 'bars, but I'd have to do that to operate switches, turn a fuel tap on etc. I'm not going to light-up at 60Mph, but in slow traffic is there a law to stop me having a Tab?
Cheers