document: First Great Western has amended some services from midday to 20:00 BST because of the expected intense heat.
  There will be no fast trains between London Paddington and Bourne End in Buckinghamshire or Henley-on-Thames in Oxfordshire.
  Network Rail said if the track buckled the line must be closed for repairs "causing considerable disruption".
  Trains from London Paddington will terminate at Twyford for a connection with a branch line service to Henley-on-Thames.
  Passengers travelling to Bourne End will see their services from Paddington terminate at Maidenhead and will also have to complete their journey on a branch line train.
  Temperatures are set to hit 30C (86F) in parts of the Thames Valley, the Met Office said.
summary: Hot weather is set to disrupt trains in the Thames Valley area with speeds being cut over fears of rails buckling.