I missed the paragraph at the bottom of the page:
"Unlike Concorde the A2 vehicle has exceptional range (approx 20,000 km both subsonic and supersonic) and is therefore able to service a large number of routes whilst simultaneously avoiding supersonic overflight of populated areas. Its good subsonic performance enables it to service conventional subsonic overland routes thereby increasing its sales potential to airlines."http://www.reactionengines.co.uk/lapcat_veh.html
"The vehicle is sized to carry 300 passengers since this is typical of future supersonic transport designs and thought to be the minimum to achieve a competitive seat/mile cost."
Boeing 777 for comparison:http://www.boeing.com/commercial/777family/longer_range/index.html
"Provisions for up to three optional fuel tanks have been added in the aft cargo area of the 777-200LR to be able to fly a range of 9,395 nautical miles (17,395 km) with full passenger payload (301 passengers)."http://en.wikipedia.org/wiki/Cruise_%28flight%29
"Typical cruising speed for long-distance commercial passenger flights is 475-500 knots (878-926 km/h; 547-578 mph)."