Other parts of London were close to gridlock as Olympic traffic restrictions began to bite.
Heathrow is expected to witness one of its busiest days ever with 250,000 travelling through including the first of the athletes and officials.
Many drivers, however, seemed oblivious to the Olympic traffic only lane which operates coming into London on the M4 between junctions three and two.
Paul Watters, AA head of Public Affairs, said there was always the risk that if some drivers witnessed others using it they would follow thinking the lane was open for general use.
He said: "It's a bit like a bus lane, if people see a lot of traffic in a bus lane sometimes they follow it into it thinking it is ok. There is always that risk.
"The number plates of cars supposed to be in the Games Lane have been recorded - just like the Congestion charge - if you haven't got your number plate on that list then you will get a penalty."
The Metropolitan Police's former head of traffic, Kevin Delaney, warned even the slightest problem on London's roads during the Olympics could create "the perfect storm" of traffic delays.
Mr Delaney, now head of road safety at the Institute of Advanced Motorists, said: "The problem with the Games lanes is that London's road network runs at, or very close to, capacity almost all day, almost every day of the year.
"Wherever the Games lanes are, they have reduced the amount of lanes for ordinary traffic. You are actually reducing the amount of road space for ordinary traffic.
"Unless everybody heeds the advice to not drive, there are problems. Imagine if there is a situation where we have a breakdown or a crash. The road network just would not cope with that.
"It would be like a perfect storm - the level of congestion that you would normally get would be magnified.
"It is because London's road network actually operates so efficiently that if anything goes wrong it goes badly wrong.
"The best analogy I can make is the blood system in your body - it works fine until you get a clot but when you do get one it has a disproportionate effect."
Only licensed taxis and members of the "Olympic Family" are allowed to use the lane which operates between 5 am and 10 pm.
The Highways Agency confirmed the lane restrictions had come into force at 5 am.
That section of the M4 has only just reopened following repairs to a damaged flyover near junction 2.
Charlie Mullins, founder of Pimlico Plumbers, warned the Olympic road closures would put immense pressure on vehicle-based businesses and even push some firms out of business.
He declared that following the opening of the M4 "Zil Lane" today his engineers will defy the regulations enter the special lanes when necessary when responding to emergencies.
The company, known for his high prices and high level of service, has in the past used Max Clifford for publicity.
Mr Mullins said: “It doesn’t matter if you run one vehicle or hundreds, if you operate a van-based business in London you’ll be hit hard and could end up going to the wall.
"Businesses will watch their income drain away as they sit in jam after jam as the athletes and dignitaries cruise by."
He added: “It’s very easy for them to shut the roads for the greater good of the Olympics and offer advice not to drive in Central London. It’s not so easy when you run a business that’s based on driving around the capital.
“That's why I'm still telling my engineers to join those elite lanes when necessary, since a burst pipe pumps out 3,000 litres an hour and that's going to cause way more damage than a 130 quid fine every time.”
Peak time traffic was at a virtual rush-hour standstill over a huge part of south east London with Olympic re-phasing of the traffic lights at the Kidbrooke interchange on the A2 being blamed.
Traffic trailed back to the Black Prince at Bexley. Conditions were described as "horrendous."
Surrounding across the south east were much more congested than usual as drivers sought unsuccessfully to get around the A2 problems.
Traffic on the A20 up from Kent was also described as being "much heavier" than usual.
Traffic lights failed on the north side of Kew Bridge causing huge tailbacks and a lorry broke down at Trafalgar Square.
On the Tube the District line, one of the busiest on the network and used by more than 650,000 people a day, service was suspended between High Street Kensington and Edgware Road due to a signal failure.
The line later reopened but severe delays continued into the peak.