The 16:40 train from Corby collided with the 15:50 service from Nottingham at about 17:15 BST, just south of Elstow.
British Transport Police confirmed that 53 people remain in hospital and eight are in a critical condition.
Passenger Pete Knapp described the crash as being “like a bomb explosion”.
Earlier Prime Minister Sir Keir Starmer said his thoughts “were with all those injured” in the incident.
He told the House of Commons: “I was deeply saddened to learn of the death of the driver of the Corby to St Pancras train.
“His family have requested privacy, and we should all respect that. I send my deepest sympathies to them at this awful time.”