Do I need to take an infant car seat on a coach?

[ladylush]

Can't seem to find any info on the internet about legislation. Am going on a day trip with the dc on Wednesday. Any info gratefully received. I don't know the name of the coach firm but can find out tomorrow.
TIA

Know you don't need one. I used to take one when I was a nanny as I had more than one child to hold. If it is easy to take one I would as it keeps the child in the seat if not don't.

Thanks Would prefer to bring one if I can fit it easily but if not at least it's not a long journey.