On 17 December at about 5.45pm, a well dressed man entered the hospital with a large, heavy bag. He walked up to reception, put the bag down and left without speaking to any member of staff.
Initially, staff were concerned the bag contained a bomb, but soon realised it held thousands of pounds in cash.
A spokesperson for Great Ormond Street Hospital For Children NHS Trust would not reveal the amount but said it was “a five figure donation”.
He said: “Obviously a substantial anonymous cash donation requires a number of checks to be made before it is accepted, and these are underway.
“If the money is associated with something criminal, the police will keep it. If not, it will be returned to the hospital.
“All donations are gratefully received.”