Harry Potter is on the triple-decker purple Knight-bus heading for SE1 soon after the dramatic opening of Harry Potter and the Prisoner of Azkaban.
The high speed journey is not comfortable but soon the vehicle is in SE1 challenging red buses on Lambeth Bridge.
The first stop is Borough Market where it pulls up in Stoney Street outside Octopus House next door to The Market Porter . A passage leads to the Leaky Cauldron pub where the architecture reflects the area's lost Winchester Palace.
In the daylight, forbidden to wander due to danger, Harry gazes out of an upstairs window at the tower of Southwark Cathedral as the market seethes below.
But soon he is at King's Cross boarding the famous school steam train for his his third year at the extraordinary Hogwarts boarding school.
Here there are extraordinary happenings and, as always with a new school year, new characters. David Thewlis as Professor Lupin and Emma Thompson as Divination Professor Sybill Trelawney give good performances. Also starring are Robbie Coltraine, Michael Gambon, Richard Griffiths, Alan Rickman, Dawn French, Fiona Shaw, Maggie Smith and Julie Walters.
The film's own stars are of course Daniel Radcliffe as Harry Potter with Rupert Grint and Emma Watson as the companions.
Surprises include St Paul's Cathedral's splendid internal staircase leading to an attic classroom.
The credits are very long but presented in a clever way. Those who stay to watch will find out where the Stink Bomb Store is.
• Harry Potter and the Prisoner of Azkaban (PG) is on general release and opens in IMAX format for the first time at the the London IMAX in Waterloo on Monday 19 July. Booking 0870 787 2525.