A second railwayman, who suffered "horrific" burns when fire broke out on a maintenance train on the Channel Tunnel Rail Link, has died in hospital.
Mr Lynch's colleagues described him as "a hero"
Douglas Lynch, 50, lost his fight for life on Saturday, four days after the fire, which also killed his colleague.
The blaze started a mile inside a tunnel under the River Thames between Swanscombe, Kent, and Thurrock, Essex.
The fire was on a train carrying cables used in the construction of a new line linking Gravesend to London St Pancras.
Mr Lynch's family sent their "heartfelt thanks" to staff at Broomfield Hospital in Chelmsford who fought to save him.
Kent Police said Mr Lynch passed away at 2128 BST on Saturday.
A statement from the family said: "We understand Dougie brought his locomotive to a stop while engulfed in fire, preventing it colliding or causing catastrophic damage anywhere else in the tunnel."
Mr Lynch apparently stayed with the train to prevent a major incident for which his colleagues have called him "a hero".
His wife Denise said: "You will not find a more health and safety conscious man which is why I find it so hard to believe that I have lost my husband, my sons his father, and his grandchildren their grand dad."
More than 50 firefighters were called to the scene after the alarm was raised at about 1915 BST on Tuesday.
A railway shunter died at the scene.
Mr Lynch suffered 90% burns to his body and was taken to Darent Valley Hospital, Dartford, before being transferred to the burns unit at Broomfield Hospital.
The fire was confined to the part of the tunnel still being built.
An investigation into the cause of the fire has been launched.