How do I check a cambelt on a 2000 rover 45?

As above.

Just bought the car, and the garage I bought it from did 12 months MOT and a service. However, on getting home we realised the back brake light wasn't working. We'd asked them to replace the cambelt, as during the service they called and said the head gasket was on its way out so they were putting that right, so I asked them to do the cam belt at our cost at the same time.

Now, as the brake light wasn't working pre MOT and not working now, we're now wondering if the cambelt wasn't replaced. Is there is simple way to check if its just been replaced?

Thanks for your help