I have made a booking on the Capitaltravel.com site but I have found a cheaper rate

Capitaltravel.com offers the following “Best Price Guarantee”. If you have reserved a hotel room through Capitaltravel.com and then show us that you could book the same room for the same dates with the same conditions at a lower rate than is viewable and bookable on another website. We will either match that rate or beat it. Here you may link to a claim policy.