The Desert Rats was the nickname of the 7th Armoured Division of the British Army which was formed in north Africa in 1938.
Orwell Park School was selected as a training base because its slope down to the River Orwell provided terrain which was similar to the water, beach and woodland of Normandy where the D-day landings took place.
Rodney Scott, chairman of the Desert Rats Association of which Camilla is patron, said: "[Orwell Park] is absolutely ideal. It had accommodation both for officers and soldiers and this is as near as they could get [to replicating beaches at Normany] without being out in the open.
"It proved to be absolutely vital because they did dismount in good order. We had very few losses compared to some of the terrible losses that some of the Americans had."
Camping by the Orwell
The regular soldiers lived in tents for 10 and they started arriving on 8 May 1944.
Apart from training, their job was to waterproof the tanks ready for landing on the beaches of northern France in water which would be three to four feet deep.
Sgt Harold 'Hal' Currie, 4th County of London Yeomanry, was a 19-year-old gun loader in a Cromwell tank who was stationed at Orwell Park.
"We were allowed to wander around the countryside but not to contact anybody," he said.
Duchess joins Desert Rats reunion
"But I think everyone knew that invasion was imminent, but no-one knew where we would be and what date it would be.
"When we left Orwell Park to go to Felixstowe [at the end of May 1944], it was quite a surprise to people living in the area to see the tanks rumbling down the road.
"We left Felixstowe to join the armada of ships off the south coast which was a magnificent sight."
Mr Currie joined the Desert Rats after the older men had come back from the campaigns in north Africa and Italy.
"I was one of the youngsters who joined them when the Desert Rats came back from the Middle East in 1944," he said.
"The older men knew exactly what they were going in for, but we youngsters could not get there quick enough.
"When you get into the battle you realise it's not just fun and games, it's a serious matter.
"I was excited. You haven't got a clue what's going to go on and perhaps in a way it's just as well, isn't it?"
Sgt Hal Currie with a Russian soldier in Berlin in 1945
The Desert Rats reunion at Orwell Park is an annual event and it involves the veterans engaging with the schoolchildren.
Headmaster Rowland Constantine said: "As far as teaching history is concerned, you try and help the children imagine how things were.
"To be here on site with the veterans gives them a real insight into how it was.
"It's an expurgated version. As far as the veterans are concerned, they will tell them about Orwell Park and war in general, but not the whole gory story."
Sgt Currie has other fond memories of his time in Suffolk.
"Not far from the school there was a farmhouse and one day I saw a lady drawing from the well and we'd have a little drink and she had a very nice daughter of about 18 years of age," he said.
"We had a sort of brief encounter - in those days just going out for a coffee or something like that.
"But we lost touch and I didn't contact again when we came back to England."
Rodney Scott, who is not an army man himself, said Orwell Park and the Normandy campaign is a vital part of the Desert Rats' history.
"Any man that puts a red rat on his shoulder now, knows that he's putting it on on the back of these boys," he said.
"Every single man that left here we offer our great thanks. For all those that we lost, we offer prayers to God that they went to him."