Taken from MSE:
2for1 Theme Parks with Persil On-pack voucher offer
Get 2for1 on a range of theme parks and attractions, including Alton Towers Resort, the London Dungeon, Madame Tussauds, Thorpe Park and Legoland, when you buy special Persil 100th birthday washing detergents.
The cheapest pack that you can get the voucher with is likely to be the 950g Persil powder, which retails at around £2.59. Unusually, this 2for1 voucher is valid at 33 different attractions, so as well as the larger Merlin theme parks youll also be able to use it at a range of local attractions.
Find one voucher on 100th birthday packs of 730ml or 1470ml Persil Small & Mighty Bio, Non-Bio or Colour, 48s Persil tablets Bio, Non-Bio or Colour, and 950g or 2.85kg Persil powder Bio, Non-Bio or Colour, while stocks last.
Cut out the voucher and bring it to the attraction to get one free admission when one person buys a full price adult ticket, valid on the day only. Expiry dates vary, but its valid at all the attractions until at least Monday 31 August 2009. There are also some exclusion dates, so remember to check these before you go.
Theres a limit of one voucher per person, per transaction. You can find the promotional packs in Tesco, Sainsburys, Asda, Morrisons and many more. See the full list of attractions and more details on the Persil website.