Keith said both Armstrong and Aldrin came into the facility for a rehearsal and to prepare for the mission.He said the pair were shown a number of solar panels they would be planting on the moon so the team all decided to sign their names on the brackets.
But Keith decided to pay homage to the UK and drew a "little Union Flag" to ensure Britain wasn't left out.
Speaking on The One Show last night, Keith said: "We got a pen and signed our names and when I signed my name I thought "I'd better put 'UK'".
"We wanted to give Brits a bit of a credit, so I thought I'd also draw a little Union Flag.
"So I've a little Union Flag sketched onto there…installed it on the experiment package and it went to the moon."