Initially they use it to make themselves comfortable through that time traveller's faithful friend: the bookmaker, then begin to explore the art, culture and science yet to come.
Keeping Lola a secret they are unable to actually change anything much beyond their own knowledge, tastes and fortunes. When World War II begins the pair turn to saving lives anonymously, broadcasting as "The Angel of Portobello": warning people of air raids and other calamities in an absolutely prescient manner.
When a young Intelligence officer tracks them down they are persuaded to turn Lola to the war effort.
No good will come of this.
Andrew Legge has an antidote to much formulaic cinema in this charming alt history/time paradox piece.
It's done in a found footage manner, nominally using an ingenious cine camera built by Martha with knowledge taken from Lola rather than the now over-familiar mobile phone or video tape you normally get in this genre and it has a look very much its own.
Yes they go over well worn time travel staples, breaking no new ground, but do it from a different angle of attack. Martha realises something very bad has happened when David Bowie no longer exists for her to watch and we are given a taste of what's to come in the artist he is replaced by. Which in her distress she pays no attention to.
Again an example of how tiny movies can often have more to offer than the box office behemoths. 8/10 highly recommended.