Currently 130,000 young people aged 13 to 22 years serve in units based in 198 private schools and 45 state schools. The Prime Minister, however, admitted that, like Mr Portillo, he never served as a cadet. He told the Commons that he opted to play cricket rather than join other pupils on parade. So what is the real and enduring value of the cadet corps experience?
The writer and poet Al Alvarez went to Oundle School in Northamptonshire and completed four years in khaki. "I do not recall the experience with any great animus," said Mr Alvarez, who edited the Faber Book of Modern European Poetry. "It was not a question of choice, you just did it, and besides, anything was better than chemistry."
He recalls the drill and the hours spent perfecting his battledress for the weekly parade. "I think they decided pretty early on that I would never make an officer. The trouble was that I stayed on for a couple of extra terms to take a scholarship, so in the end they made me Regimental Sergeant Major. When I saw the film If, it was exactly as I remembered it. What it would be like now I have no idea, but in principle I am not against it," said Mr Alvarez.
John Mortimer has a less benign recollection of his days in the cadet corps at Harrow. "The whole thing was the most ridiculous waste of time," according to the creator of the fictional lawyer, Rumpole of the Bailey.
"I remember we had to go on some sort of exercise on a common near Aldershot, and while everyone else was crawling around in the mud I sat under a tree and read the plays of Ibsen. After a while a man on a white horse came up and said, 'Bang bang, you're dead'. I said, 'Thank you very much' and went back to Ibsen.
"Quite what the Government think they are up to with this scheme, heaven knows, especially at a time when half the country is terrified by the nation's youths. I think this is an hysterical gesture by a party desperate to cling to power."
The writer and broadcaster Edward Enfield went to Westminster School, where all the boys had to join either the Scouts or the army cadets. "I was always a completely inefficient soldier," said Mr Enfield. "I regarded the experience as part of my overall education, just as I did later when I completed my national service. Real soldiers used to come to drill us. It was quite amusing to see these sergeants from the Brigade of Guards reduced almost to tears because some of the boys used to rag about, and there was nothing they could do to discipline us.
"I regarded it as a chore, though one of the boys I used to give orders to ended up as a Major General, so I expect he enjoyed it well enough."
He believes that if the scheme is well-administered, some teenagers will benefit. Mr Enfield's own son, the comedian Harry Enfield, did not join, however. "I don't think that would have been quite his cup of tea," said his father.
One of the schools with the strongest cadet tradition is Eton, but even there attendance is not compulsory. Old Etonian Nicholas Coleridge, now the managing director of publishing house Conde Nast, worked hard to keep out of the ranks.
"I unhesitatingly elected to do social service. I enthusiastically dug old women's gardens, and for a while I supervised a very popular stamp club in Slough," he said. "The corps was extremely popular with those people that like that sort of thing. Most of them went on to become farmers in Scotland, I believe.
"However, when this scheme was first mentioned, I mildly surprised myself by thinking it might not be such a bad idea. I think that, provided it is kept on a voluntary basis, a lot of people will enjoy it. Besides I have a strong suspicion that it would evolve into a glorified 'outward bound' exercise with a lot of hiking and camping."
The television personality and sports journalist Michael Parkinson was amused to be asked about life as a schoolboy soldier. "Did I enjoy the cadet corps? Don't be daft," he snorted. "I went to Barnsley Grammar. We didn't have anything like that and besides, we all left there as fully fledged guerrillas."