London has an undeserved reputation as a rainy city, with “things to do” when the U.K. capital is wet a popular topic of conversation among tourists.

But this year could see that image shattered in dramatic fashion, with much of southeast England gripped by a serious drought currently affecting about 20 million people.

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Restrictions on the use of water were imposed Thursday from the southeast coast to the River Humber in the north and almost as far west as Wales.

By the time the Olympics comes to London in July, further controls could be introduced that will prevent aircraft, London’s famous double-decker buses and other vehicles from being washed. Other restrictions are also likely.

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Those arriving for the greatest show on Earth, may find a parched, somewhat grubby city. The event itself, however, will be exempt, so rest assured there will be water in the diving pool, the rowers will not in find themselves marooned and the smiles of the synchronized swimmers will remain fixed.

Driest 2-year period since 1884
In an attempt to prevent the situation getting worse, seven English water companies imposed a so-called "hosepipe ban" Thursday – mainly designed to reduce the amount of water used in people's yards -- and urged people to cut back on water use by, for example, reducing time spent in the shower to just four minutes.

Ignoring the ban could result in a fine of more than $1,500.

“We have now received below-average rainfall across our region for 20 of the past 25 months, making it the driest two-year period since records began in 1884,” Martin Baggs, chief executive of Thames Water, said in a statement.

“Imposing restrictions on the use of [hoses], although regrettable, is the most sensible and responsible next step in encouraging everyone to use less water so we can maintain supplies for as long as it stays dry, and reduce the risk of more serious restrictions later in the year,” he added.

Hilary Murgatroyd, a spokeswoman for Thames Water, which supplies London and surrounding areas, said if the hosepipe ban did not produce the required effect, companies could decide to implement a more Draconian measure: the “drought order.”

This would mean that cleaning of aircraft and public transport vehicles would be prohibited, apart from “washing require for health and safety reasons,” she told msnbc.com.

“It [a drought order] is something that we’re considering, but it will be dependent on the reduction we see over the next couple of weeks and what the weather does, what rainfall we get,” Murgatroyd added.

Despite its wet reputation, London gets about 23 or 24 inches of rain a year; New York City regularly gets twice that amount.

'Nothing too torrential'
Charlie Powell, a meteorologist at the U.K.’s Met Office, told msnbc.com there was no sign of an imminent downpour over the drought-affected areas.

He said that little rain was expected to fall over the next few days although about 0.4 inches was expected Monday “in a few places.”

“Nothing too torrential. Anything is better than nothing at this stage, but no significant, prolonged rainfall,” Powell said.

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He said that March had been particularly dry with much of the U.K. as a whole receiving less than half the average rainfall for that month.

This came after a winter that saw eastern Scotland and south and eastern England receive about 75 percent of average rainfall, while northern Ireland and the north and west of Scotland was particularly wet with 120 percent.

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One regularly mooted solution to drought in the south is pipe water from Scotland, which usually has plenty to spare.

But Murgatroyd said this was not a “practical” option: water is heavy and therefore expensive to move and also has a different chemical makeup in different places due to the type of rock and treatments used to make it drinkable that could cause problems in the pipes, such as corrosion.

Warmest March on record for dozens of cities

Last month, saw a desalination plant open in East London, which will take sea water from the Thames Estuary and turn it into enough water for a million people.

But the question remains, will British people pull together, let their prized hydrangeas wilt in the sun and put up with being slightly less well washed?

One indicator could be how willing people are to report neighbors who break the hose ban to authorities.

According a non-scientific poll in The Guardian newspaper at 10:50 a.m. ET, more than 70 percent would not. 

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