A driver of a train which crashed into buffers was suffering from fatigue, an accident investigation has found.
The woman was coming to the end of a "relatively demanding night shift" when the collision occurred at London King's Cross station at 6.23am on August 15, the Rail Accident Investigation Branch (RAIB) said.
Four passengers and one member of staff reported minor injuries in the 4mph crash, which pushed the buffers back by over one metre, according to the report.
The four-carriage train involved was the 5.13am Great Northern service from Royston, Hertfordshire.
The driver, who was not identified by the RAIB, "briefly closed her eyes because they felt tired" in the seconds before the collision.
When she opened them she made an emergency brake application but it was too late to avoid hitting the buffers.
The RAIB revealed that it was her first night shift after a period of rest days and she was "not sufficiently well rested".
It noted that the Rail Safety and Standards Board "advocates a limit of eight hours for the first night shift" due to concerns over fatigue, but the woman's shift was due to be 35 minutes longer.
The driver told the RAIB that her tasks were "more intensive than other night shifts" with less opportunity for rest.
She had two years' experience of driving trains on the lines out of London King's Cross.
Speaking on the day of the crash, passenger Natasha Coella, 36, said: "We just all went flying. It's as if while we were slowing down it kind of accelerated again.
"No one expected it and people just went from one end of the carriage to the other."
A spokesman for Great Northern's parent company Govia Thameslink Railway said: "Our internal investigation of this incident has not reached its conclusion, so we are not able to comment on the details.
"We take fatigue issues very seriously and strive continuously to improve in this area in line with industry good practice."