The best and worst train operators for being able to access the internet have been identified by a major survey.
Great Northern and Southeastern are joint bottom of the rankings for the reliability of internet connections on board, with just 18% of passengers satisfied.
Southern is the third worst with a score of 22%, followed by Merseyrail (24%), London Overground (25%) and Northern (27%).
Heathrow Express achieved the highest satisfaction score for the ability of its passengers to secure a reliable internet connection at 71%.
Grand Central is the runner-up at (68%), ahead of Hull Trains (61%) and Chiltern Railways (51%).
Passengers were asked to consider both the provision of onboard wi-fi and their ability to stay online using a mobile or tablet.
The overall satisfaction score across all operators in Britain was just 30%, with more than half of passengers (56%) describing themselves as "dissatisfied" with the web connection on their journey.
This was the second worst score out of all 38 satisfaction measurements.
Only the availability of power sockets scored lower at 25%.
Transport Focus head of policy Mike Hewitson said internet access is the third most important thing that passengers aged 16-25 want to see improved, ahead of punctuality.
He told the Press Association: "One of the benefits of rail travel is it allows you to do things in a way that driving or being on a plane doesn't.
"That means connecting with people, doing work, checking emails or chatting on Facebook.
"What really drives people batty is when you get the connection and it drops out.
"It's got to be reliable. It's no longer a treat. It's become essential and an expectation."
Mr Hewitson said the results of the research show the reliability of internet connections on trains is "still patchy".
He continued: "There are commitments for new rolling stock to have better wi-fi provision.
"When we get that we'll see a difference, but there will be a transition for a while.
"You're not going to get much wi-fi on a Pacer train, but the replacements will be much more equipped."
It is the first time that internet connections have featured in the survey, meaning there is no historical comparison.