This A28 adaptor allows the fitting of 28 Watt 2D lamps into conventional bayonet lampholders. This boxed example is believed to have originated from the Ministry of Defence; hence, the additional barcode label attached.

Opening the box reveals the adaptor, an instruction sheet and (beneath the lower sheet of cardboard) a lamp.

The adaptor consists of a plastic cylinder with a standard bayonet cap on one side...

...and a GR10-q lampholder on the other. Please tell me that I am not alone in thinking that this lampholder resembles someone with a particularly "nonplussed" face!

The very carefully-placed identity label carries Thorn EMI branding; suggesting that the unit was manufactured between 1984 and 1987.

Releasing the three captive screws in the unit allow access to the Thorn G69603.4 choke. The wiring is very simple thanks to the lamps incorporating a built-in starter - one wire links the bayonet cap to the incoming live terminal of the choke; another connects the ballast to the 2D lampholder; the third connects the 2D lampholder to the other connection on the bayonet cap. As all of the components are arranged in series in this circuit, there is no need to check polarity at the lampholder before fitting the adaptor. Judging by the marks located either side of the choke, it appears that the adaptor could be connected directly to a BESA conduit box, rather than having the bayonet cap fitted.

The supplied lamp dates from December 1990.