I've got a new job in london and i'm not sure if the quoted salary includes 'London Waiting' - can anyone help

I have been offered a new job in london and they have informed me of the salary i will be on - however they didn't say if this included 'london waiting'. I was wondring if anyone knows how this works - for example, do all businesses in london exclude LW when quoting salaries or not - and also how much is LW. Enlighten me (serious answers only):