Plus, you can't see gear indicators at night.
I've greatly improved the low-light readability of various Shimano trigger shifters by carefully dismantling the indicator module and adding a sliver of white Scotchlite tape to the visible side of the pointer. Another strip on the outside alongside the window provides a reference.
It works stupendously well under the light of the feeblest of head-torches, and being white (rather than red) is generally visible under street lighting, even by specular reflection. That covers about 95% of my nocturnal cycling - some guesswork can be required for the remainder. A worthwhile improvement for 10 minutes work and a homeopathic quantity of Scotchlite.
No idea how conducive the Brompton design is to such treatment...