The entrance to the British Museum of London it is free, because it is funded by the British Crown. However, at the entrance you can see some mailboxes ready for the tourist to leave a donation. It is suggested that this amount to 3 pounds sterling, although of course it is not mandatory. You have all the information in: «Do you have to tip in London?«.
You have all the information in: "Do you have to tip in London?".