Thank you for your further response. Commodore Clipper sailings from Portsmouth, due to length of the sailing may not be suitable to meet a 4pm departure to Sark, however we have sailings from Poole that would be arriving into Guernsey before this time, on the majority of crossings. Further information on timetables can be located at:
https://www.condorferries.co.uk/import/pdf/UK-to-Guernsey-Timetable.pdf
Our contact centre team will also be happy to advise on timetables and relevant sailings.
Kind regards
Condor Ferries