The world’s two most senior surviving moonwalkers, Buzz Aldrin and Alan Bean, the second and fourth men respectively to walk on the surface of the moon, were the big names from the Apollo lunar landings who came to London for the latest Autographica event.

Four crew members from various space shuttle missions were among other guests at the event last month, held a mile from Heathrow airport. It made for an interesting gathering in which stories about the NASA space programme were recollected by those who had actually taken part in the missions.

At the a formal dinner during the weekend event, which attracts autograph collectors and those interested in past and present space programmes, Mr Aldrin got up to give a short talk on the future of space exploration. He went on to speak about his vision for the colonisation of Mars, and he likened it to the pilgrim fathers aboard the Mayflower sailing ship in 1620 who left England and reached what is present day Plymouth, in Massachusetts, to establish the second English settlement in North America. Just as they had not waited to get a ship back to England, so the eventual first colonisers of Mars will not seek a return journey to Earth, Mr Aldrin predicted.

Looking back over almost 50 years since the lunar landing programme it is important to remember that such great achievements were made with technology that would be labelled archaic in today’s world, and how astronauts in that earlier era completed missions that would, in all likelihood have been aborted nowadays.

There were plenty of reminders of this during the course of the weekend as stories were told. Space Shuttle astronaut Bruce McCandless was working at mission control during the Apollo programme and was one of the key contacts for Apollo XI astronauts Neil Armstrong and Buzz Aldrin during their landmark first landing on the moon.

At the dinner Mr McCandless recounted the launch of the follow-up Apollo XII mission, which included among the crew fellow guest Alan Bean. As the Saturn V rocket soared upwards through the Earth’s atmosphere it was hit by either lightning or a self-induced electrical discharge. “They lost all power to the command module,” said Mr McCandless. “The computer in the Saturn V redundant for the very first time, so they switched over to the backup computer and they kept on flying. It was Alan Bean who painstakingly restored power to the command module, brought the fuel cells back online and shortly thereafter they made it successfully into orbit, aligned the platform, got a go to proceed to the moon and had a very successful mission.

“And I think that in today’s environment we have probably become so risk adverse that had we had a similar incident with the shuttle we would have insisted on immediately terminating the mission and coming home. It’s a real tribute to Alan and Pete Conrad and Dick Gordon that they were able to salvage the mission even after a near catastrophe like this.”

On the earlier Apollo XI mission that ultimately put Mr Armstrong and Mr Aldrin on the moon’s surface there were a few touch-and-go moments. As Armstrong piloted the lunar module towards the moon’s surface and its designated landing site it became increasingly clear that the chosen site was strewn with more rocks and boulders than had been anticipated.

Mr Armstrong skilfully avoided the unfavourable terrain and headed for a smoother area in the Sea of Tranquility, however an alarm was activated inside the landing module indicating a critically low level of propellent to fly the craft. The two astronauts held their nerve and despite having an apparently depleted propellent tank continued to the favoured landing spot. The Eagle landed and Mr Armstrong and Mr Aldrin made their historic moonwalks on July 20, 1969.

It was later discovered the module had slightly more landing propellent than the indicator had registered, an estimated 30 to 45 seconds’ worth. The ‘sloshing’ of the propellent inside the tank had resulted in the premature activation of the alarm. It was a fault that would be remedied after the follow-up Apollo XII mission a few months later.

At 84, Mr Aldrin is remarkably active and sprightly. His popularity at the event was evident as he signed autographs and posed for pictures, never appearing overwhelmed or tired. He used a selection of felt-tipped pens to sign autographs, something that was instructive of another incident on that maiden moon landing.

After returning to the lunar module having walked on the moon’s surface, Mr Aldrin and Mr Armstrong faced a potential hazard that placed a question mark over whether they would be able to lift off to rejoin Columbia, the lunar orbiter being piloted by Michael Collins, and head back to Earth. Mr Aldrin noticed a broken circuit switch on the floor of the module. It was the switch that was needed to activate the ascent engine to lift off from the moon. Mission control was informed of the problem. After a short sleep, and with no solution forthcoming from mission control, Mr Aldrin took a felt-tipped pen from a pocket on his spacesuit and placed it into the opening where the broken switch should have been. The pen fitted and worked as a makeshift circuit-breaker allowing the module to lift off.

Of all the lectures given by the guests during the weekend Alan Bean, the fourth man to walk on the moon, was the best attended. Indeed, the organisers noted it was a bigger lecture audience than they had seen at any of the previous 19 Autographica events. Mr Bean described how he had gone on to forge a career as an artist, painting space mission scenes and striving for accuracy, which brought him to a story about his painting of Neil Armstrong on the moon.

The painting was among those exhibited at the Smithsonian National Air and Space Museum, Washington DC, in 2009 to mark the 40th anniversary of the moon landings. In attendance were many Apollo mission veterans, including Mr Armstrong. One of the guests studied Bean’s painting and spotted Armstrong was portrayed wearing a wristwatch. The guest wasn’t convinced that Mr Armstrong had worn his watch on the moon’s surface and said so to Mr Bean, who was caught off guard by the observation and wondered if he had got the detail wrong. Bean suggested the guest go and find Mr Armstrong, who was elsewhere in the museum, and ask him if he had been wearing a watch.

It should be pointed out here that there are very few photographs of Mr Armstrong on the moon because he was the one issued with the camera during the mission. As a result most of the iconic moon landing photos show colleague Mr Aldrin on the surface. There is one full-body picture of Mr Armstrong on the moon, however, he has his back to the camera and it is not clear if he is wearing his watch or not.

The inquiring guest tracked down Mr Armstrong and asked him about Mr Bean’s painting and whether or not he had worn a wristwatch on the moon’s surface. Mr Armstrong said, “Has Alan painted me wearing one?” The reply was “Yes,” to which Mr Armstrong responded, “Well, that’s how it was.” It was a good answer, but it wasn’t how it had been on the moon. In reality Mr Armstrong had taken off his watch and left it inside the lunar module as a backup because the on-board mission timer was not working. Many months later, having researched the facts himself, Mr Bean painted out the watch from the portrait.

Five-times astronaut and space shuttle commander Robert ‘Hoot’ Gibson talked about his experiences and answered questions during the weekend. I asked what it was like to experience the fiery descent back through the atmosphere on the return to Earth. He described the glowing flames that filled the view outside the windows, and how the crew prepared for the increasing heat inside the shuttle by reducing the interior temperature considerably in the two hours immediately prior to re-entry.

Hurtling back to Earth at Mach 25 (that’s 25 times the speed of sound) also meant a great deal of braking and slowing was required to execute a safe, unpowered landing. Mr Gibson explained how, as the shuttle decelerated from supersonic speeds to subsonic (going below Mach 1, or 760 miles per hour), the sonic shock wave trailing the craft caught up and, starting from the rear of the shuttle, moved through the fuselage and up to the front where the flight deck cabin would momentarily shake and vibrate.

Mr Gibson is a talented photographer and took some stunning pictures of fellow shuttle astronaut Bruce McCandless during his historic, first untethered spacewalk in 1984. Mr Gibson and his wife Rhea Seddon, another shuttle astronaut, were both at the Autographica event and gave joint lectures about their space missions, which included a selection of family photos taken by Mr Gibson of their youngest child standing in the desert at the Edwards Air Force Base, California, watching as a space shuttle, with his mother a crew member on-board, came in to land.

At a low-key pre-event drinks reception Buzz Aldrin stood on a light bridge in the hotel’s atrium, where he casually spoke to a number of attendees. A few days later I watched an excited dad speaking to his son overseas via a video link on a tablet device and asking Mr Aldrin, who was walking past, if he would greet his son. Mr Aldrin obliged with a salute into the tablet’s webcam.

There were plenty of memorable offbeat moments, such as astronaut Mr McCandless light-heartedly noting during the dinner event that if NASA had had someone with as much glamour as ‘Space 1999’ actress Barbara Bain as a real life astronaut (Ms Bain was one of the weekend guests) there probably would not have been any space programme funding cutbacks.

Autographica is a twice-yearly event held in the UK.