Yes, but the average number of people in a car at a place like Alton Towers is probably 4, so that equates to 20,000 people. 1800pph minimum does not meet these needs considering that the majority of guests are trying to enter the park at a similar time (or if they aren't then they end up doing so because of the queue).
On a different note (and rant ), I think that the opening times for Towers are appauling, especially for a bank holiday weekend!
Thorpe and Chessie are open until 6:00pm, Blackpool Pleasure Beach until 8:00pm and then 6:00pm on Monday yet Towers still shut at 5? (Doesn't look like it will improve later in the year either judging by the website bar scarefest - 6pm in summer holidays is awful).
This is not on for a theme park who consider themselves to be the UK's greatest.
I don't think so!
If Blackpool Pleasure Beach (which imo is a far, far better park but doesn't have the vast amount of money as Merlin parks) can open until 8pm then why the hell does towers shut at 5?! And they wonder why they aren't getting people through the gates!