London's iconic Trafalgar Square fountains will be switched off over the summer to comply with the strict hosepipe ban.
Thames Water has ordered the supply be cut last night as part of a blanket restriction, which includes ornamental fountains, designed to conserve drought-hit reservoirs.
The Greater London Authority said the current water stocks feeding the fountains will run out at the weekend.
Negotiations are underway to see if a compromise can be found in time for the arrival of millions of tourists to Trafalgar Square during the Olympic and Jubilee summer.
Bans on hosepipes for 20million people in the drought-hit South and East of the country came into force yesterday, ahead of a drizzly weekend for the North and West, but more sunshine in the South.
Water firms say the ban is likely to last until the autumn if not into next year, even if there is normal rainfall during the summer.
This March saw just 37 per cent of the long-term average rainfall in all of England and Wales, according to the Met Office â just a little above last year which was the driest March on record whilst February saw just 46 per cent of the average.
An Anglian Water spokesman said: âIt's not beyond the realms of possibility it will carry on into next year.
âEven if it is a rainy summer, a lot of the rainfall is absorbed by plants and it does not help boost our supplies after two dry winters have left our reservoirs and aquifers very low.
âWe have to be realistic and responsible, and will lift them as soon as we are able.'
Southern Water said the ban was likely to last the whole summer and could carry on into next year, unless there were weeks of continuous heavy downpours.
Richard Aylard of Thames Water said: âRealistically it will be in through the summer into the autumn, as summer rain doesn't do much. Unless we have a particularly wet summer.'
In the summer of 2005, a hosepipe ban imposed on 12million people mainly in the South East was not lifted by all suppliers until the following January after a rainy festive season.
Anglian Water last imposed a hosepipe ban in the summer of 1990 â it lasted 15 months.
Seven water companies have banned the use of hosepipes and sprinklers to water the garden, wash vehicles or boats, clean patios or any other surfaces or for recreational purposes.
Watering cans still be used, and there are exemptions for blue badge holders and cleaning for safety reasons.
But the Environment Agency warned hosepipe bans were ânot a silver bullet', and urged business to clamp down on washing cars and windows to save water.
Groundwater levels are lower than during the drought of 1976 in parts of Shropshire, the Chilterns and the North Downs, and reservoirs are extremely low.
Public fountains â including London's Trafalgar Square, which was set to be a centrepiece of the Olympics after a ÂŁ200,000 refit â will be turned off this weekend when their current supplies run out.
While there have been two years of chronic low rainfall, enough water for 20million people is leaked by water companies every day.
Yesterday the Daily Mail revealed bosses of water companies which are imposing hosepipe bans took home ÂŁ4million in bonuses in the last financial year (2010-11), including those who failed to meet leakage targets.
They even handed a ÂŁ500million windfall to mainly foreign shareholders in September 2011 after the drought was declared.
Water bills rose by up to 8 per cent at the start of this month, squeezing living standards in households even further.
The average rise was 5.7 per cent to an average of ÂŁ376, which is just above inflation.
But Southern Water, which has one million customers, hiked bills by 8.2 per cent and Thames Water, which has nearly 9million customers, by 6.7 per cent.
Conservation groups have welcomed the ban. Phil Burston of the RSPB said: âReducing demand now will help keep more water in the environment, keeping rivers flowing for longer and protecting their precious wildlife.'