I saw an interview with him when he spoke about piloting the Lunar Module on Apollo 10, which was a rehearsal for Apollo 11, including everything except the final descent to the lunar surface, that is, the un-docking from the Command Module and going into orbit around the moon. He said that if he was tempted to do the descent and land on the moon, to claim the glory, NASA had deliberately not fuelled the Lunar Module on Apollo 10 enough to make the descent, to deter him (whoever was the Apollo 10 pilot), so he could only go into orbit, and fly over the moon's surface, then re-dock with the Command Module. As it happened, Neil Armstrong landed the Lunar Module with 17 seconds of fuel left.