fitting an sso sideways

[electric ian]

I have encountered a 90degree sideways mounted socket in washing machine space during a PIR, it's been fitted like this as plastic pipe is too close to it to allow a plug to be inserted in the usual way.

During my 17th ed college course such a scenario was discussed and the course tutor stated that it was permitted by regs as long as no excessive/abnormal strain would occur to the cable of any plug that will be plugged into it.

does anyone know the regulation number that states this please?

thanks