You use latest or last to talk about one of a series of events which is continuing to happen, or one of a series of things which someone is continuing to have or produce.
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◊ events
If one of a series of events is happening now or has just happened, you refer to it as the latest one.
The latest closure marks yet another chapter in the history of Gebeit.
You refer to the event before the latest one as the last one. If no event of the kind you are talking about has happened recently, you refer to the most recent one as the last one.
...the weeds that had grown since the last harvest.
◊ things you have or produce
If someone keeps having or producing a series of things, you refer to the one they have now or the one they have produced most recently as their latest one.
...her latest boyfriend.
...his latest novel, `The Comfort of Strangers'.
You refer to the one before their latest one as their last one. If they have not had or produced one recently, you refer to their most recent one as their last one.
Loach has not been idle since Family Life, his last film for the cinema.
You can talk about more than one thing in this way by putting last in front of a number. For example, you can talk about `his last three books'.
Her last two pictures have been disasters.
Useful english dictionary. 2012.