“The vessel is now headed to Dubai, where it will refuel before beginning a months-long journey around the horn of Africa, through the Mediterranean and to the shores of Syria.”
The Grace 1 oil tanker was seized by Royal Marine commandos in a landing in darkness off the coast of the British overseas territory on July 4.
Britain rejected the idea that it could release a Iranian tanker in exchange for a British-flagged vessel seized by the Islamic Republic in the Gulf.
Iran has already seized a UK tanker in response and London has said it will attempt to protect its ships from more Iranian harassment.
Also on Sunday, Iraqi Prime Minister Adel Abdul Mahdi has ordered an investigation into a strike against a Popular Mobilization Force’s (PMF) base this past weekend.
Oman urged Iran on Sunday to let the British-flagged tanker Stena Impero, which it seized on Friday, depart.
"Our reaction will be considered but robust."
Tehran has denied any involvement in the attacks near the Strait of Hormuz, a major transit route for global oil supplies.
Fox News and CNN revealed that a US drone was targeted by an Iranian missile during the June 13 tanker incident and that a drone was downed over Yemen by Iranian-backed Houthis.