I am conducting some research on my grandfather, who was a German Jew who escaped Germany and eventually served for several years in the British Armed Forces. He did not become a British citizen until 1947, however.

I am just curious as to what he would have been classified as. I have found this source from the BBC, that reads:

Internment of civilian nationals belonging to opposing sides was carried out in varying degrees by all belligerent powers in World War Two. It was also the fate of those servicemen who found themselves in a neutral country.

At the outbreak of war there were around 80,000 potential enemy aliens in Britain who, it was feared, could be spies, or willing to assist Britain's enemies in the event of an invasion. All Germans and Austrians over the age of 16 were called before special tribunals and were divided into one of three groups:

• 'A' - high security risks, numbering just under 600, who were immediately interned;
• 'B' - 'doubtful cases', numbering around 6,500, who were supervised and subject to restrictions;
• 'C' - 'no security risk', numbering around 64,000, who were left at liberty. More than 55,000 of category 'C' were recognised as refugees from Nazi oppression. The vast majority of these were Jewish.

The situation began to change in the spring of 1940. The failure of the Norwegian campaign led to an outbreak of spy fever and agitation against enemy aliens. More and more Germans and Austrians were rounded up. Italians were also included, even though Britain was not at war with Italy until June. When Italy and Britain did go to war, there were at least 19,000 Italians in Britain, and Churchill ordered they all be rounded up. This was despite the fact that most of them had lived in Britain for decades.

Thousands of Germans, Austrians and Italians were sent to camps set up at racecourses and incomplete housing estates, such as Huyton outside Liverpool. The majority were interned on the Isle of Man, where internment camps had also been set up in World War One. Facilities were basic, but it was boredom that was the greatest enemy. Internees organised educational and artistic projects, including lectures, concerts and camp newspapers. At first married women were not allowed into the camps to see their husbands, but by August 1940 visits were permitted, and a family camp was established in late 1941.

That many of the 'enemy aliens' were Jewish refugees and therefore hardly likely to be sympathetic to the Nazis, was a complication no one bothered to try and unravel - they were still treated as German and Austrian nationals. In one Isle of Man camp over 80 per cent of the internees were Jewish refugees.

More than 7,000 internees were deported, the majority to Canada, some to Australia. The liner Arandora Star left for Canada on 1 July 1940 carrying German and Italian internees. It was torpedoed and sunk with the loss of 714 lives, most of them internees. Others being taken to Australia on the Dunera, which sailed a week later, were subjected to humiliating treatment and terrible conditions on the two-month voyage. Many had their possessions stolen or thrown overboard by the British military guards.

An outcry in Parliament led to the first releases of internees in August 1940. By February 1941 more than 10,000 had been freed, and by the following summer, only 5,000 were left in internment camps. Many of those released from internment subsequently contributed to the war effort on the Home Front or served in the armed forces.

I do not know if he had been interned in a camp and eventually released to fight, all I know is that he only became a British citizen in 1947.

My question is: did serving in the British Armed Forces automatically make him a British citizen, or could he have served as a 'refugee'?