The captain of the AM Ghent has been prosecuted for the oil spill which occurred off Gibraltar last month.
In addition to a £20,000 fine, the ship's owner has had to pay a £1.5 million pound security bond to cover clean-up expenses.
The spill occurred on 12 February in Gibraltar port, and the AM Ghent's captain confirmed that one of its venting valves had failed while bunkering.
A counter-pollution plan was put into immediate operation and a clean-up began, but the oil affected numerous sea birds and some of the spill still remains in areas north of the harbour.
These accidents are rare, but they come at great environmental cost. Gibraltar's Environment Minister, Dr John Cortes, said at the time, "Over the last ten years the marine life in our harbour had come back in strength and it was becoming a key wildlife area.
"This is a significant setback which we are monitoring closely and we are working hard to minimise the impact as much as possible. But it will take time to recover."