A First Great Western service approaches Princes Risborough. It is on the down line over Saunderton Summit; the line curving to the left is the up line through Saunderton Tunnel. 43196 and 43088 are heading for Weston-super-Mare but the line out of London Padidngton is closed for engineering work so they are taking the route through the Chilterns to reach Didcot where they can regain the Great Western Main Line.