The London Metro of 12 June carried a photograph and a brief report of the sixth annual Tomatina festival in Boyaca, central Colombia, where 20,000 revellers helped ‘farmers celebrate a 15-tonne crop [of tomatoes], the largest in the country’.
Tomatina festivals, at which participants pelt each other with tomatoes [Solanum lycopersicum, formerly Lycopersicon esculentum] seem to have originated in Bunol, near Seville, Spain, where since 1944 a festival has been held on the last Wednesday in August each year. According to the London Evening Standard magazine of 1 October 1999, the festival began ‘when a group of youths, unhappy that their effigy failed to win a prize at the summer fair got into a scuffle with the winners. Market stalls were overturned and lo and behold one of them was piled high with ripe and juicy tomatoes; great for hurling.’
In 1997: ‘More than 100 tonnes of tomato projectiles fly through Bunol – painting the town red and impregnating it with the smell of tomatoes. Residents cover their homes and shopfronts with plastic, but there is little they can do to prevent the entire plaza from becoming stained with the crimson puree’ [1].
The festival seems to fascinate newspaper picture-editors and frequent reports appear in the British press [2].
A version of La Tomatina has been held in London at least once, in 1999, at the Redback Tavern, Acton, which caters mainly for young travellers from Australia and New Zealand:
‘After six hours of pre-fight drinking, the mainly antipodean crowd donned goggles and protective headgear and, as the hooter sounded at 5 p.m., descended on the heap of tomatoes in the centre of the converted volleyball court.
Neighbours, protected from the flying fruit by plastic sheeting, peered from their windows in disbelief as men … rugby-tackled victims, sending them skidding through as sea of tomato sauce …
After 15 minutes the fight was over’ [3].

1. London Evening Standard, 28 August 1997.
2. See, for example, Guardian, 31 August 2006; Independent Magazine, 1 October 1999; Telegraph, 17 August 2002; The Times, 26 August 1993, 31 August 1995, 29 August 1996, 26 August 2004; Western Daily Press, 26 August 2010.
3. London Evening Standard, 31 August 1999.

Image: La Tomatina, Bunol, Spain, August 2010; Wiki Commons.

Update:  The Metro of 9 June 2015 carried a photograph of a young man lying  in tomato pulp at the Boyaca Tomatina festival, where ‘some 32 tons of the fruit were used in the food fight, which is much smaller than the original one on Brunol, Spain.’