steve rosenberg, bbc news, moscow. a jury at the old baileyf the moment a bomb partially exploded on a tube train in south west london. some of the passengers have been describing in court, how their hairand clothes caught fire, in the packed carriage, last september. thirty people were injured at parsons green station. ahmed hassan who's 18, denies attempted murder. june kelly has more. the moment when a fireball engulfed a packed train carriage. it left passengers burning and screaming in pain, the old bailey heard today. this is ahmed hassan, the teenager on trial for the attack. here shopping at asda the day before, and being asked for his id. he bought batteries and screwdrivers. hassan is an 18—year—old asylum seeker, and the following morning cctv showed him leaving his foster parents' home in sunbury, in surrey. other cameras captured his journey as he carried a little plastic bag, said to contain his bomb. at wimbledon station he went into the toilets, where it's alleged he set the timer on the device, and then he made for an undergro