Twisting and taping was never an acceptable method.
The main cable is a stranded twin & earth type from the 1970s, and provides power to socket outlets.
The joined cable at the side has been added by someone to provide power to an additional socket outlet.
The other thin cable visible at the back is from a television aerial, and the metal pipe across the top of the picture is for gas.
This circuit passed all of the usual tests perfectly, which shows the value of inspection, rather than just testing.
This joint and the cables were just hanging under the floorboards, with no support or fixings at all. The earth floor below was very wet.
This is just normal insulation tape - not waterproof or even water resistant.
This was originally connected to a 30A rewireable fuse, and the smaller cable is 1.5mm² - far too small for a 30A circuit.
No financial saving either - although a junction box was not required, an extensive amount of insulation tape was used instead.
The stranded wires are tinned copper, as was common in the 1970s.
The other cable is solid core copper, and could have been added at any time from the late 1970s to the mid 2000s.