Fluorescent Under-Aircraft Exhibit Lights

In the "Cold War" hanger at the Royal Air Force Museum at RAF Cosford, the aeroplane's undersides are illuminated by these portable lighting units.

They feature the aircraft's name and there are several under each one so you can get a good view of the underside.

The ones shown are under the wings of a legendary Handley Page Victor B2 nuclear bomber, one of three designs that formed the UK's nuclear "V-Force" in the 1950's and 60's.

The inset picture on the aeroplane's landing gear door is a photo from the top showing the grid diffuser which prevents the lamp from being viewed directly off-axis.
Inside is basically a normal 4 or 5 ft T5 fluorescent batten.