At the time, he was in command of an artillery regiment, chasing the retreating Germans across the Rhineland. Passing a wooden gateway, his eye was caught by some railway wagons in a siding.
By an odd chance he had seen similar wagons in Normandy several months earlier, when he had liberated a trainload of Jews bound for Germany. His suspicion aroused, he went to investigate and found that the wagons contained what he describes as "very recent bodies".
He reported to his brigadier that he believed the gate might lead to a concentration camp and asked permission to take a look. The brigadier, anxious to press forward, gave him two hours. So it was that Belsen was discovered.
Fifty years ago this month, the first of the death camps were liberated by the Russians as they swept through Poland. Belsen was not found until April, but it was the only camp liberated by the British Army, and it was from there that the newsreel imagescame which scarred the minds of a generation of Britons. Bob Daniell saw it all first.
He entered Belsen by smashing through the gates in his tank and then knocking down the first building he came to, sending Germans fleeing in all directions. Then he parked and got down, to find himself looking into a trench 150 yards long, and filled with naked bodies. "Parts of the corpses kept moving. You would see an arm rise, then a leg, and sometimes whole bodies would come to the surface. This was the natural gases and acids from the bodies at work. "
Instructing his men to have their breakfast (an order which, unsurprisingly, they found it impossible to obey), he set off "very foolishly" alone to see what he could find.
Behind the first door he broke open he found the camp hospital, a hangar full of bunk beds eight tiers high. Every bed was occupied, but 90 per cent of the patients were dead, many of them drowned in excreta from the beds above. All had been too weak to move. "The sight and the smell were completely appalling; they were all completely naked and many of them no doubt had typhus. I didn't stay to see more. I left the door open and found a guard to show me the rest. "
He visited three more buildings. In the first two were hundreds of people, as thin as skeletons, in the last stages of starvation.
"The hangars were foul. The smell was perfectly appalling. They had not been cleaned out for at least two months. The occupants themselves were incapable of moving, let alone of cleaning out the straw. "
Hearing shots in the distance he made his way to the perimiter wire to find that a group of prisoners who had attempted to escape were caught on the wire. Half a dozen Hitler Youths were amusing themselves by pulling these people down and shooting them, "not to kill, but to cause the most pain. They were shooting the men in the balls and stretching these naked women out and shooting them in the crotch. It really was an unspeakable sight. I shot four of the Hitler Youth and the other two ran away. "
Bob Daniell is certain that in his two hours at Belsen he never lost control, but this was the nearest he came to an action in the heat of emotion. "I was extremely tough. I had already fought one war in the desert and I was very used to coming across armed men. Unless they were visisbly trying to kill me I normally would not have shot them, but with these men, their actions were so appalling that I did, without hesitating. "
He next saw the gas ovens, which had been cleaned out because there was no fuel to run them. This was why there were so many corpses lying around: in the previous fortnight no fewer than 9, 000 people had died in the camp, of starvation, typhus, dysente r y and other diseases.
"It was pathetic. There were worn paths to each of the gas chambers and on the side a pile of spectacles at least six feet high. "
Returning to his tank, Bob Daniell summoned another unit by radio, instructing them to bring medical and diet teams.
"There were at least 3, 000 inmates still just alive. They were all starving, and skeletons to look at. The irony of the whole thing was that outside the wire was the most fertile part of the German Rhineland, with fields of potatoes and green vegetablesof every kind. Inside the wire the only thing there was to eat was a pile of rotting potatoes.
"My two hours were up and I had to go and rejoin the 29th armoured brigade. That was the last I saw of the appalling sights of the Belsen Jewish death camp. I was very glad to leave. "
What mark did Belsen leave on him? He insists he has never lost sleep over it. In war, he says, "you either become very tough or you can't go on."