-Temperatures as low as Himalayas overnight, plunging to nearly -11C in Buckinghamshire and Oxfordshire
-Heavy snow expected in Cumbria, Lincolnshire, East Anglia, North Yorkshire and the Peak District
-Drivers warned to prepare for cold weather and check 'gritter Twitter' updates
-Highways Agency clocks up a million miles gritting roads
-Breakdowns attended by AA double and British Gas puts fleet of 4X4s on standby as call-outs soar
-Salt stocks across Britain stand at 2.4m tons - a million more than last year
-Sporting events called off including Portsmouth v Hull City Championship football match
By DAMIEN GAYLE, COLIN FERNANDEZ and EMMA REYNOLDS
Frosty morning: Angela Lurssen braves the chilly water in Hyde Park's Serpentine early today, as the country awaits inches of snow
The icy weather that has caused chaos across Britain is set to continue with forecasters expecting widespread snow of up to 15cm deep.
Temperatures plunged as low as the Himalayas overnight, reaching -10.6C in Chesham, Buckinghamshire and -10.3C in Benson, Oxfordshire.
The Met Office issued a severe weather warning and the AA attended double the usual number of breakdowns yesterday as the exceptionally mild winter suddenly turned into the reverse.
Goosebumps: More bold bathers steel themselves against the freezing waters of the Serpentine
Taking the plunge: A man in a swimming cap dive bombs the Serpentine while a woman in a wide-brimmed hat lowers herself in slowly
The freezing conditions have seen daytime temperatures plummet four or five degrees lower than average for February - traditionally the coldest month of the year.
British Gas have a fleet of 4X4s ready to help households where heating problems could put their health at risk after emergency call-outs doubled.
Widespread snow is expected this afternoon and evening in areas including Cumbria, Lincolnshire, East Anglia, North Yorkshire and the Peak District and temperatures will remain low, with -9C expected in the snowy Midlands.
Solid ice: The summer resort of Sandbanks turned into Siberia today as Poole harbour froze over and boats became trapped in ice
Misty morning: Confused seabirds walked on the frozen water as the channel ferry chopped its way through the icy sea
No day for fishing: Poole harbour was filled with jagged chunks of ice after a sub-zero night hit most of Britain
Submerged: A man of a hardy constitution stretches out beneath the water's surface
Water and woollies: Steph Cox grits her teeth and dons a furry hat for a Serpentine swim, while a boy wrapped up in socks and jacket rests his scooter in the shallows
'Wales and the South West along with parts of western Scotland will mostly see rain. There will be rain for Northern Ireland as well but I think elsewhere we are looking at risk of snow.
'It should clear away south eastwards by tonight. It will probably clear all but the far South East and East Anglia by dawn tomorrow.'
Numerous sporting events were hit by the bad weather with Portsmouth's home match against Hull City the first Championship football fixture to be cancelled because of a frozen pitch.
Extreme swimming: Committed Miss Lurssen jumps in the fridge-like water for some lengths when few would dare
Cosy cuppa: The swimmer warms up before her test of endurance, her hot drink steaming beneath the winter sun
Snowy slopes: A lorry gritting the road on the A4059 near Hirwaun, in the Brecon Beacons, Powys, Wales
Elemental: While the gritters work below, a group of daring mountaineers climb ice above in the Brecon Beacons, Powys, Wales
'Motorists are being advised to check the latest weather and gritting updates on council websites and "gritter Twitter" feeds, as well as refresh themselves on winter driving guidance and what to stock in their car,' he said.
'Information about school closures and bin collections is also being updated regularly online.
'Thousands of new grit bins have been placed in estates and side streets, residents have been given their own bags of salt along with salt spreaders in some neighbourhoods, and arrangements have been made with parish councils, community groups, snow wardens and farmers to grit hard-to-reach areas.
Don't slip! A fell walker admires a frozen waterfall at Fisher Gill in the Lake District yesterday
Deep and crisp and relaxing: Wild Ponies enjoy the snow in the Quantock Hills in Somerset
Frozen London: Seven snow-white birds swim past ice-encrusted reeds at the Serpentine in Hyde Park yesterday
The AA said there had been more than 4,300 breakdowns nationally this morning - a whopping 1,300 per hour. It is expecting 16,000 calls by the end of the day, which is almost double the 8,500 it receives on a normal Saturday.
A spokesman said: 'This is similar to what we had yesterday, and we are expecting the same tomorrow. The million-dollar question is how severe the snow will be.
'Ice can be more of a hazard, by snow and rain can turn into ice, meaning the ground takes longer to thaw.'
The AA advised drivers to pack cold weather provisions including food and warm clothes, and take out a fully charged mobile phone.
Frosty: A car windscreen freezes in the UK yesterday as temperatures plunged as low as -11.1C yesterday
A spokesman for British Gas said the company had received more than 200,000 calls in the last five days, compared with 120,000 to 140,000 during a normal winter week, and was expecting a further 50,000 this weekend, compared with the 20,000 normally expected in the winter.
He said: 'With the roads becoming treacherous across the country, British Gas's fleet of nearly 100 4x4s will help British Gas to meet its customer commitment, to make same-day visits to Homecare customers who have no heating or hot water and report the problem before 1pm.'
Ice, ice baby: Frozen in full flow, this dramatic waterfall at Fisher Gill in the Lake District appears still to be frothing and bubbling, as fell walker Martin Campbell looks on in wonder
And it's freezing cold down south, too: The fountain next to Westminster Bridge demonstrates how low the temperatures have dropped in central London
Quick, where's Nelly's thermals? An elephant fountain display outside a garden centre in Marks Tey, Essex is covered in ice after the freezing cold night
BELGIUM: The Grand Palace and Grote Market square in Brussels are covered in snow and, right, the weather causes a traffic jam in Namur, Belgium
AMSTERDAM: A canal is frozen over and, right, a man pulls his child on a sledge in Dam Square
Not great weather for ducks... Ducks swim in the icy waters of St. James's Park in central London
'It's worth as well if you are visiting friends and family then tell them when to expect you,' he added.
But when warmer weather returns, there is likely to be a new set of problems, with the AA warning road users about a likely increase in potholes when conditions thaw out.
Paul Watters, head of roads policy at the AA, said: 'After several days of sub-zero temperatures, we’re expecting a rash of potholes when the current freeze ends. The cold penetrates deep into the road surface, which can collapse when it thaws out, creating a pothole.
'Road users, particularly those on two wheels, will need to be on the lookout, especially on secondary roads. Damage to wheels and tyres is quite common, so if you notice any unusual steering or other driving characteristics, get the vehicle checked at a garage or tyre specialist.'
The icy weather has even hit Rome, with snow falling in the Italian capital for the first time in 26 years.
Clucking freezing: But these chickens will keeping warm in their very own woolly jumpers at Green Meadow Animal Sanctuary, Pattingham, Wolverhampton
And when in Rome... make sure you wrap up warm
Anyone fancy an open top bus tour through Rome? That Italian capital was hit by its first snowfall in 26 years stopping visitors from entering the Colosseum, the Roman Forum and the Palatine Hill, the former home of Rome's ancient emperors
Fashion comes first, whatever the weather. These pictures were taken in Rome, where despite the city's first substantial snowfall since 1986, the two ladies pictured eschewed sensible shoes for their usual high heels. Elsewhere in the city they were taking things more seriously. Tourist sites such as the Colosseum and the Forum were closed on health and safety grounds.