How to get National Theatre tickets for £10

On Friday’s the National Theatre has a “Friday Rush” where they offer tickets for unsold seats to shows the following week for just £10 per person. The way it works is that at 1pm on Fridays, the countdown timer on the National Theatre’s Friday Rush page becomes a button and you press it to be allocated a random number in the queue.
If the number is below 100, you stand a decent chance of getting some cheap theatre tickets, although it can be worth staying in the qu