The chancellor appeared to be particularly impressed by the showcased range extenders, small combustion engines used to increase the range of electric cars.

That can probably run forever. In fact, I think that the idea of a rentable range extender trailer plus EVs that have some kind of rear trailer charge port that’s usable while driving — the regular one isn’t, to keep people from accidentally driving off from a charging station with the thing still plugged in — does a lot to make EVs more usable. If doing an occasional long-range trip just means going to U-Haul and renting a range-extender trailer, that does a lot to eliminate the range restrictions imposed by batteries.

https://en.wikipedia.org/wiki/Range_extender