Well, the WTS coordinate press releases in the local press as well as providing the text for the Amex website.
You can read the text here:
http://www.eventsatbhafc.co.uk/whats-on/Jehovah-witness-convention.php
All of these press releases state 10,000 people were expected but the actual was no where near that.
The last speaker, Stephen Morris of the British Branch Committee made a big thing about two people that had turned up as a result of the invitations. This is all well and good until you consider that even if you said that 5000 of those in attendance had distributed 10 invitations each (a highly conservative estimate IMHO) that would be 50,000 invitations. Two attendees from 50,000 invites - a 0.004% return rate. What a joke.