A white plug which has a switch and neon indicator in the top.
The fuse is accessible via a red plastic tray, and allows the fuse to be changed without removing the lid of the plug.
Age is unknown - the presence of the 'new' coloured insulation isn't helpful here, as blue/brown has been used for appliance flexes since the 1970s.
This is probably caused by heat from the neon making the plastic brittle.
The neon is completly black, evidence that it has been switched on for a very long time.
Although the switch lever is in the lid, the switch mechanism is located in the base.
Fuse in this example is a 5 amp BS1362, branded JoJo.