Extending cables - correct connections

I would like to join two lengths of twin/earth lighting cable inside a deep recessed metal wall box (will still have a switch fitted to it, not a blank faceplate). The joined cable will effectively run behind the switch - not connecting to it.

Can I use simple "chockblock" to make the join? If not, what?

(for info, I'm adding an additional intermediate switch (switch B) between two existing intermediates (switches A and C).

A is currently connected to C (via 2 x T/E), and I wish to wire as A to B to C. Simplest route is to run a new cable from switch A to new switch B. To get from B to C I want to run back to location A and join to the previous A to C cable).

If the connection is accessible in the box you can use a terminal strip (aka choc block).

If not accessible the joint must be crimped or soldered.

Thanks for the quick reply - nice and simple!

While choc block can be used, it would be nicer to use crimps - there's far less chance of some unsuspecting owner in the future coming along to try and replace the switch, and deciding to undo some of the connections in the choc block and then getting incredibly confused...