On 24 to 26 July special heritage loco hauled trains will run on the Metropolitan Line London Underground- this is a very rare opportunity (the first since the Pandemic) to enjoy the Sarah Siddons and her train.
https://www.ltmuseum.co.uk/whats-on/heritage-vehicle-outings/metropolitan-line-sarah-siddons
On the Saturday it includes a rare opportunity to travel the north curve to Watford (Met)- a stretch of track only normally served before 6am, or at around midnight.
With ongoing re-signalling on the Met it may even turn out to be the last chance for this treat.