In message , Jarle H Knudsen
writes

Is it possible to visit Stonehenge by public transportation from London as
a one day excursion?

While it is possible, it is worth noting that many people find
Stonehenge rather disappointing unless they have a specialist interest.
I'd consider combining it with a visit to Salisbury Cathedral (possible
via rail and bus) or with a visit to Bath. Several coach companies offer
day trips to Stonehenge + Bath from London for a reasonable price.

--
Paul Terry