After a weekend of travel disruption nationwide and beyond, the working week is beginning with yet more delays and cancellations.
Faults with Network Rail’s signals are affecting the highest number of travellers.
The Stansted Express service has shut down for the morning, with passengers to and from the UK’s fourth-busiest airport urged not to travel.
A fault with the signalling system means no trains are likely to be running to or from Stansted airport until the afternoon.
Rail passengers on the East Coast main line connecting Scotland, Yorkshire and commuter stations north of London with King's Cross are facing delays of up to 90 minutes because of a signalling failure at Welwyn Garden City.
The problem is affecting commuter services on one of the busiest lines in the country.
The Thameslink through central London is in chaos. Confused rush-hour passengers at London St Pancras and Blackfriars stations were given contradictory and misleading information about the best way to reach their destination.
With delays of an hour or more reaching Gatwick airport, some travellers’ flights are jeopardised.
Many other problems created by Storm Dennis are continuing. There is extensive disruption across the Transport for Wales network, with no trains on the mid-mid-Wales line from Shrewsbury to Aberystwyth and Pwllheli. The Heart of Wales line between Swansea and Crewe is out of action.
There are also delays between Southampton and Bournemouth, Swindon and Bristol Parkway, and on local lines in the West Midlands.
Many ferry services are disrupted, with no Caledonian MacBrayne sailings from Oban to Barra, Coll and Tiree.
Flights are returning to normal after hundreds were cancelled at the weekend, particularly on easyJet. But Sunday’s IT failure at Heathrow is causing many knock-on delays and cancellations.