Grelco 2 Amp double adaptor
One 2A plug to two 2A sockets.
This adaptor allows two 2A plugs to be used in a single 2A socket.
Three pins, BS546.
Due to the way the second outlet is angled, the adaptor is very compact - the earth pin of the plug in the side socket passing between the L&N pins of the plug in the end socket.
The three adaptors shown are all identical ...
... which does inevitably lead to people overloading the original socket by using a stack of these unfused adaptors.