I've been to this restaurant many times over the years, the last two times the service and food has been much improved compared to previous visits.
This combined with the current offer of 50% off main courses made the last visit absolutely superb value.
Food was really quite good, starter a little disappointing but acceptable, steak was huge and truly mouth-wateringly good (T-bone) - one of the best steaks I've had in the UK, ever!!
Bottomless soft drinks and chips/potatoes make even the normal prices good value.
Right next door to Chessington World Of Adventures, this is an ideal place to go for a meal after a day at the theme park, but it will be busy if you don't arrive early so be prepared to wait.