Two weeks before the start of the Olympic games, the London organisers are facing problems over security and travel arrangements. The British government has called up 3,500 military personnel because the contractor has failed to supply enough trained security staff for Olympic venues.Ministers have promised more immigration officers at London's Heathrow airport after complaints about long delays.The transport planners are looking at alternative routes into the capital after the motorway between Heathrow and the centre of London had to be closed for emergency repairs.