A woman suffered a fatal head injury while leaning out a train window below an inadequate warning sign, an accident investigation has found.

Bethan Roper, 28, died on the Great Western Railway (GWR) train near Twerton, Bath on December 1 last year after suffering a head injury.

She was leaning out of the window of a door when her head was struck by a tree branch while the train travelled at around 75mph.

The door was fitted with an opening window to enable passengers to use the handle on the outside when they needed to leave the train.

A report by the Rail Accident Investigation Branch (RAIB) found that a warning sign above the droplight window met industry guidance but “did not adequately convey the level of risk”.

The sign featured the word “caution” with the message: “Do not lean out of window when train is moving.”

Investigators claimed the use of the word “caution” suggested that leaning out the window could be done safely if care was taken.

They also highlighted that it is much smaller than other signs around it and its background colour was yellow, when red would have been more appropriate for conveying danger.

Following the death of a passenger leaning out a window on a train in south London in August 2016, GWR completed a risk assessment of its droplight windows.

This resulted in a plan to install enhanced warning signs with a red background by May 2018, but this had not happened by the time Miss Roper was killed seven months later.

GWR told investigators it did not meet its schedule as two staff members involved in the task left the company and a system which tracks pieces of work failed.

The signs were updated following the death of Miss Roper.

The RAIB also noted that Network Rail, which is responsible for managing lineside vegetation, had not undertaken a tree inspection of the area since 2009 and this is “possibly causal to the accident”.

Miss Roper was on board the London Paddington to Exeter service while returning to Penarth, South Wales from a Christmas shopping trip with friends.

The report stated that one of the group opened the window and at least one other friend leaned out before Miss Roper, who was struck by the tree branch at 10.04pm and pronounced dead at Bristol Temple Meads station a few minutes later.

She worked for the Welsh Refugee Council charity and was chairman of Young Socialists Cardiff.

Her father, Adrian Roper, released a statement after her death saying his daughter “enjoyed life to the full whilst working tirelessly for a better world”.