Today marks the start of the busiest travel weekend of the year with an estimated 2.5 million people leaving the UK for the long weekend and the school half-term holiday.
Many millions more will stay in the country travelling around Britain but journeys home and abroad could be jeopardised by anyone from railway engineers to the Pope.
Rail travel to London on a number of lines will be disrupted through the weekend. Stretches of Britain's busiest railway, the West Coast main line, will be closed for the next three days. The biggest problems are north of Crewe, with journey times between Liverpool and the capital doubled.
In Derbyshire, the line between Derby and Chesterfield will be disrupted through half-term, with delays and diversions for passengers on East Midlands and Cross Country trains.
Rail passengers between Scotland and London are being urged to use the East Coast main line, though no extra trains will be laid on.
Anyone hoping to reach the capital by other means were warned: "Don't drive into London unless you have to" by Transport for London. "Roads around St James's Park are closed from 1 June to 5 June inclusive."
National Express has laid on 7,000 extra seats to and from London, with the busiest services from Bournemouth, Bristol and Birmingham.
Travellers heading abroad face a host of problems. The Foreign Office warns of a spate of armed robberies and "express kidnappings" by eastern European gangs in Belgium, particularly near the Channel ports. "They have been robbing victims on the spot or taking their victims under force to the nearest cash machine."
Baggage handlers employed by Swissport will strike on all four days of the jubilee weekend and Ryanair, the biggest airline at Stanstead, warned passengers it "may not be able to accept checked in baggage on some or all flights".
Pope Benedict XVI is due to visit Milan this weekend, and has chosen to fly rather than travel by rail from Rome. As a result, easyJet is warning of "potential disruption at Milan Linate airport" from today until Sunday, and urges passengers to allow extra time reaching the airport.