I thought this was a joke when someone told me about it – a temporary 12m swimming pool will be in Euston/Camden from Monday 29th April until Thursday July 11th.
Total Swimming's aim is to teach 1,200 people how to swim through community swimming programmes. Lessons are free of charge, but tickets are, of course, limited. Please see the website for more info.
Additionally (something I noticed in this week's Time Out), the pool is available outside lesson time during the evenings and at weekends for just £2 entrance fee, though you still need to book.