In First, you need an empower plug.
In New Club World (the fan shaped divider), you need an empower plug.
In New New Club World (translucent plastic divider), you need and a US plug or a UK to US adaptor.

The empower plug looks like the cigarette lighter in a car but you can remover the top bit and there is a smaller plug inside that works (see top part of picture in the link). Unfortunately the bottom part of the picture is the connection to a Apple MacBook Pro laptop. The same empower plugs works on AA and VS. If you google "airline adaptor" you can see where to get one.

You cannot use UK plugs on BA