Floods, signal failures and even animals on rail tracks have combined to hold up millions of travellers as the Christmas getaway began.
Flooding affected a number of rail services, which were also delayed when animals got on to the line near Micklefield in Yorkshire.
One of the worst of the delays was due to a signal problem at Hayes & Harlington in west London.
This caused long hold-ups to those travelling by rail to Heathrow on the west London airport's busiest day of the Christmas period.
Buses had to replace trains due to flooding on a number of lines, while on the London Underground the whole of the Jubilee Line was closed at the start of services due to a signalling system problem.
The Jubilee Line was up and running with delays by the heart of the morning rush-hour, but other Tube travellers had to contend with severe delays on the Bakerloo Line due to a signalling failure at Paddington in west London.
Today was the busiest day on the roads as well. Those setting off early faced a number of flooded routes, with the Isle of Wight and Brockenhurst in the New Forest, Hampshire, particularly badly affected. One lane was closed on the busiest section of the M25 - at junction 15 near Heathrow - due to an accident.
On the railways, flooding near Ellesmere Port on Merseyside meant buses had to replace trains between Ellesmere Port and Hooton. Buses also had to be laid on between Bridge of Orchy and Crainlarich in central Scotland due to a landslip.
No trains were able to run between Crewe and Chester in Cheshire due to flooding, while floods were also the cause of the bus replacement that had to operate between Uttoxeter and Stoke-on-Trent. The flooding also led to disruptions to services in the Derby and Nottingham areas as well as hold-ups between Chester and Wrexham General in north Wales.
Heathrow was handling 123,000 passengers today, with a further 114,000 departures on Sunday and 88,000 on Christmas Eve. British Airways was also having its busiest day of the holiday period today, with 111,000 travellers getting away for the Christmas break.