usa – Can an American travel to France through the UK with a negative Covid test?

In October with the latest Covid travel restrictions update, is the flight Boston > London > Paris possible for a US Citizen in possession of a <72h negative Covid test ?
Do I instead have to quarantine in the UK for 14 days and then go to France ?
I have an AirBnB planned in France for longer than 14 days in which I will be quarantining upon arrival