Details now showing LNER Gresley A4 Bittern in charge of this service, Bittern is a sister engine and same shape streamlining as Mallard
34067 46201 46233 60019: Waterloo-Woking-Guildford-Havant-Salisbury-Bristol and return
[60019 replaces 46233 34067 and 46201 which are all unavailable]
this seems to be confirmed by there being a movement today (5th) by 60019 from the National Railway Museum at York to Southall yards.