The customary Bank Hoiday ritual of traffic jams, delayed rail journeys and thundery showers could persuade nearly two million people to depart these shores this weekend.

With, according to the RAC, up to 18 million cars expected on the roads and meteorologists predicting cool, rainy weather and gusty winds, travel agents said that they were expecting one of the busiest weekends of the year.

The Association of British Travel Agents reckons that over the long weekend, which begins half-term for schools, 1.9 million holidaymakers will leave the country. The Canary and Balearic islands would be the most popular destinations, the association said.

Back in this country several big sporting events are scheduled. The RAC said that there would be disruption on all routes leading to Wembley Stadium, where the football play-offs are being held, and the Millennium Stadium in Cardiff, where the rugby union Heineken Cup Final is being played on Saturday.

Other key traffic hotspots are likely to include roads leading to the West of England, from northern England to North Wales, and between the Midlands and Norfolk.

Iain Vale, who is RAC patrolman of the year, said: “We're all disappointed that none of the home nations are going to football's Euro 2008 tournament, but this weekend will be the start of many sports fans' summers. It's important for motorists to be aware of all the events which are on and to plan their routes around them, allowing 50 per cent more time for their journey.”

He continued: “This is also the weekend that RAC patrols really see traffic to holiday resorts pick up with the start of half term.”

More than a fifth of the rail network will be shut down, with big engineering works affecting key lines such as the West Coast Main Line between London and Glasgow. Network Rail said that £45 million-worth of improvements were

being carried out. Tens of thousands of West Coast Main Line passengers will face disrupted journeys from tomorrow as the upgrade of the line continues.

There will be no Virgin Trains or London Midland services in and out of Euston station in London on Saturday, Sunday or Bank Holiday Monday.

Two further days of work will be carried out on the Trent Valley line between Rugby and Stafford.

Other big projects include platform extensions at Luton Airport Parkway and signalling works at Merthyr and Newport, in South Wales.

The weather is predicted to be wet and thundery over much of England and Wales.

A Met Office spokesman said: “There's a north-south split. The South of England will be cloudy, wet and windy, with the possibility of thunderstorms. But anywhere in England and Wales could see rain. Basically, it's not going to feel nice.

He added: “The best of the weather is over Scotland and Northern Ireland, where it will be fine and dry. But it's not going to be a scorcher anywhere.”

Yesterday the port of Dover was reopened to ferry traffic after French fishermen blockaded the ports of Calais, Dunkirk and Boulogne.

A P&O spokesman said that services were now running at 80 per cent of normal frequency. “We want to get the freight backlog on the M20 out of the way tonight so we can get ready for the Bank Holiday tourists,” he said yesterday.

“We will be back to normal, touch wood.”

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