at Frome (specifically Main line services) L: London (on services from Cardiff and Swansea or Cheltenham Spa) M: Exeter to Bristol TM and/or the North (or Swindon to Westbury) O: Worcester/Gloucester to Weymouth/Salisbury via Bristol TM P: Worcester, Oxford and Didcot Parkway to Paddington R: Barnstaple/Okehampton to Exeter Central Services S: Used for Cross Country services to Scotland T: Heathrow Express Services and Paignton to Exmouth U: Cardiff from Taunton/WSM W: Worcester/Great Malvern/Hereford Y: Heathrow Express Services, and Local services between Bristol TM and Weston-super-Mare Examples from the Scottish Region include A: Aberdeen B: Edinburgh G: Fife, including Fife Circle via Dumfermline, and Longannet power station H: Inverness I/O: Cathcart Inner/Outer Circle, respectively R: Express services between Glasgow Queen Street and Edinburgh (even numbers eastbound, odd numbers westbound) T: Glasgow (trains from the north) Y: West Highland Other regions can use these letters for different areas, but the inter-regional codes have the same meaning throughout the country. In 2007, a special letter Q was introduced for track recording trains, such as the Network Rail New Measurement Train. This emphasises to signallers that the train is to run its booked route as it is recording, not to be diverted without the prior knowledge of the controller. Prior to this, trains operated by British Rail Research Division used the letter T. The letters X and Z are generally reserved for special use – see Special numbering. Individual identifier Because there are many trains of the same type heading for similar destinations (for example, most expresses to Scotland have headcodes beginning with 1S) the last two digits are used to separate individual services or to indicate the route (generally for suburban services). Examples The 06:09 CrossCountry service from Bath Spa to Glasgow Central is an express passenger service, so it is a class 1 train. It is going from the Western to the Scottish region, so it is given the letter S for its destination. It is one of the first services in the day, and so its headcode is 1S35. The 09:00 London North Eastern Railway service from London King's Cross to Edinburgh Waverley is an express passenger service, so is a class 1 train. It is going to the Scottish region, so is given the letter S. Its headcode is 1S09. The 22:00 Avanti West Coast service from London Euston to Crewe is internal to the Midland region, so it uses