Oyster cards

In 2003, Mayor Ken Livingstone invented the Oyster card - a credit-card sized piece of plastic that harnesses the power of clockwork and wafer-thin magnets to allow commuters to pre-pay for their travel on London's Tube, bus and zeppelin network.

Oyster card users simply press their cards against the 'no fuss' magnetic readers at the beginning and end of their journey, allowing them to pass swiftly through the ticket barriers with the ease of a top forensic detective slipping through the police line at the scene of a murder.

However, such convenience comes with a terrible responsibility - you must 'touch in' at the start and 'touch out' at the end of every journey. If you do not, Transport for London will summon one of nine St. James's Ticket Wraiths (SKILL 12, STAMINA 24) and dispatch it to your house. Probably the most eldritch of all London Underground staff, these fell, robed creatures materialise in commuters' bedrooms in the dead of night, looming over their victims and breathing out evil vapours from the very lungs of the Northern Line. The terrified Londoner must press their Oyster card against the apparition's face - which is a fully-functional magnetic reader with a wireless link to the main Transport for London database - or pay a £20 on-the-spot fine.

If you have you been affected by a visit from one of Transport for London's St. James's Ticket Wraiths or are having trouble paying your fine, call the Mayor of London's office on 020 7983 4100.