Probably about right. It's right through the centre of town so regardless of your own usual average speed, you've got every traffic light and slow motion nodder in London to contend with.
If you have any choice in the matter, get a nearer hotel. I really don't see the point of making life hard for yourself. As well as "London traffic" you also have the problems of navigating an unknown city.
Im going to be staying in a hotel near the Olympic Park and need to be near Richmond station for 10am.
GoogleMaps is saying it will take 1hr 20mims to cycle, how accurate is that?