A question of respect (let the flaming begin...)

[BBROWN1664]

Just for you then Simon.

133
If you need to change lane, first use your mirrors and if necessary take a
quick sideways glance to make sure you will not force another road user to
change course or speed. When it is safe to do so, signal to indicate your
intentions to other road users and when clear, move over.

and can be found here https://www.gov.uk/general-rules-all-dri...133-to-143