How should the situation be handled if an individual needs to self-isolate (quarantine) for 14 days following a return from an overseas trip?

The UK government advises against non-essential international travel, except to countries and territories listed as exempt. The list of exempted destinations can be found here. The UK government announced that from Monday 8 June new rules have been put in place for entering the UK because of COVID-19, apart from those countries and territories that are exempted (see above link). The rules are for both residents and visitors. When these rules are in place, everyone will need to provide their journey and contact details when they travel / return to the UK and they will not be allowed to leave the place they are staying for the first 14 days that they are in or have returned to the UK.