UK emergency services hold big Olympics test Feb 22 04:48 AM US/Eastern LONDON (AP) - Britain's police and emergency services are holding a massive Olympics security exercise centering on a mock emergency on the London subway system. The two-day test beginning Wednesday will start at the Aldwych tube station - a subway stop that has been shut to commuters since 1994. London Underground maintains the stop so it can be used in movies and rented for parties. The security test envisions that an emergency takes place on the two busiest days of the 2012 London Olympics. Authorities declined to reveal the exact scenario in advance, since dealing with a surprise is part of the test. The test is a part of an effort to create confidence ahead of the games beginning July 27 and ending Aug. 12.