On these dates the Bakerloo Tube line will be closed between Queen's Park and Harrow & Wealdstone in North West London.
While that will affect few tourists, fewer trains will run over the whole line (including in central London) as one of the two depots will be inaccessible, so there will be longer wait times, and thus busier trains.
The Bakerloo line reopens on 18 August.
This work will also affect the London Overground trains between Euston and Watford Junction- these are the all stations trains, not the fast trains which go to points further afield. The fast trains are the ones usually used by Harry Potter visitors.
That work lasts until 25 August.