Cold war era saw 200 jets scrambled each year to check out 'unidentified flying objects'

That fell to zero after the collapse of the Soviet Union in 1991 as Moscow stopped sending anti-submarine aircraft and spy planes into British airspace. But the RAF continued to scramble aircraft in missions against known targets, including hijacked airliners, suspected drug smugglers and jets launched from a Russian aircraft carrier.

The information is revealed in a Ministry of Defence briefing note for a response to a July 1996 Parliamentary Question from Martin Redmond, then Labour MP for Don Valley in South Yorkshire. He asked how many times RAF aircraft had been scrambled or diverted from tasks to investigate "uncorrelated targets" picked up on radar.

Details were included in a background note, which explained: "Prior to the demise of the former Soviet Union, aircraft were scrambled some 200 times annually to intercept and investigate uncorrelated tracks penetrating the UK air defence region from the north.

"These invariably proved to be anti-submarine or long range reconnaissance aircraft of the then-Soviet air force, some of which had already been intercepted by adjacent air defence systems or intelligence sources." The last scramble of that type took place in Septem-ber 1991.

The files also show a gambler appealed to the government for help after a bookmaker refused to pay out on his 100-1 bet that aliens would land on Earth, newly-released files reveal today.

The punter had 17 placed with Ladbrokes on extra-terrestrials being found dead or alive by the end of the 20th century. But the bookie would not pay out because the United Nations had not confirmed the existence of aliens.

Asked to intervene, the Ministry of Defence (MoD) agreed there was no evidence of visits by lifeforms from other planets and backed Ladbrokes.

The appeal is recounted in declassified MoD UFO files made available online by the National Archives. The man, from Beeston, Leeds, who was not named, placed a successful 2 bet on West Germany winning the 1990 World Cup at 6/1. His winnings were added to a 3 wager on "aliens to have landed (dead or alive) on Earth before December 31 1999" at 100/1, meaning he stood to win 1,700 if extraterrestrials were found.

Ladbrokes wrote to him in April 1999: "We advise that at present your bet is not a winner as the United Nations, who we use as our source of authenticity, has not yet confirmed the existence of aliens. However, as the bet stipulates 'before December 31 1999', should the United Nations confirm this before that date we will be only too pleased to make payment."

The punter said he had found 19 books in Leeds Central Library

reporting the Roswell incident, in which an alien spaceship was

reported to have crashed in the US in July 1947.