"Piggy Backing" circuits in DB

[dialect]

My apprentice has come back from his two weeks in college and told me that the tutor said
"To add in an extra socket, you can piggy back a 2.5mm T&E cable into a 2.5T&E ring in a 32amp circuit breaker" which would leave 3x 2.5 cables.
First I thought he had misheard but he has notes and diagrams, albeit copied by him, from the class.
Im doubting my own knowledge now, as this is something I would not do and would put as "requires improvement" on an inspection, and have not got time to trawl through the regs, right now. Any body have a opinion on this or know or can cite whether this would be allowed or contravene regulations?

[ian2]

think of it as a spur off a ring you have exactly the same just at a socket

[spinlondon]

Have a look at Appendix 15 in BS7671.