A friend reports:

"Had a 20% fare increase today. I generally have a Zones 1 and 2
period travelcard and travel out to St Albans by buying a cheap day
return from the edge of zone 2. Slightly less than buying it from West
Hampstead, That option has gone now so that my fare went up from £6.20 to
£7.50."

Why such a large increase?

--
Colin Rosenstiel