How much does it cost to travel from London to Rome on the train?

Taking a trip to Euroe and wondering how much it costs to take the train from...

London to Rome
Rome to Paris
Paris to London

Or should I go to Paris and then Rome?

Thanks!

those are really great places to visit! i've been there but we never take the train. it might not be a good idea.

You can fly for $60 EU and have a day to do what ever you like!