A fleet of French fishing boats has headed for St Helier harbour after threatening to blockade the Jersey's main port over a post-Brexit fishing row.
The UK has sent two Royal Navy ships to Jersey "as a precaution".
HMS Severn and HMS Tamar are sitting off Jersey's south west coast (blue), while the Marine Traffic map showed dozens of French fishing vessels (orange) near St Helier Harbour.
Marine Traffic image at 7.15am
Photo: Macio Agostinho
The vessels entered the harbour and let of flares before returning to open water behind Elizabeth Castle. It's understood they were demanding a Jersey government official comes out to talk to them.
One displayed a sign that read "Don't change anything. Let's stay friends. Jersey Government steal our historical wrights (sic)."
The Commodore Goodwill freight shipm which docked in the island earlier, remains in port.
Condor boss Paul Luxon described her as 'trapped' and said they are putting safety first.
Downing Street confirmed Boris Johnson spoke to Chief Minister Senator John Le Fondre on Wednesday evening the threatened blockade of the port, and the urgent need to de-escalate tensions.
"The Prime Minister underlined his unwavering support for Jersey. He said that any blockade would be completely unjustified. As a precautionary measure the UK will be sending two offshore patrol vessels to monitor the situation."
In a statement Senator Le Fondre and Minister for External Relations, Senator Ian Gorst said they were 'expecting a peaceful demonstration'.
"The responsible Ministers and government officials have met this evening (Weds) to ensure that the very best plans are in place to ensure Islanders interests are properly protected at all times. We remain confident in our ability to do this.
"Diplomatic efforts will continue to resolve the outstanding issues relating to fishing licences and to de-escalate the situation, and we will continue to liaise closely with UK and EU officials over the coming hours and days to achieve a pragmatic solution.
"Jersey’s essential infrastructure will not be disrupted as local facilities are able to meet our power requirements in the event of any external interruption."
Several islanders too an early vantage point to watch the French vessels make their approach
A Ministry of Defence spokesman confirmed HMS Severn, described as being able to mount fishing vessels for inspection, and HMS Tamar, one of the Navy's newest warships, were being deployed to Jersey "to conduct maritime security patrols".
"This is a strictly precautionary measure and has been agreed with the Jersey Government," he added.
France earlier threatened to cut the island's electricity off and French fishermen threatened to blockade the main port of St Helier to prevent supplies from being delivered.
French officials also said they will be closing their Channel Islands' offices and will stop importing Jersey products into France.
France has accused Jersey of imposing extra licence conditions, in breach of the Brexit trade agreement. Maritime Minister Annick Giradin told the country's parliament they were "ready to use these retaliation measures".
"With regards to Jersey, I would remind you, for example, of electricity transmission by underwater cable. So, we have the means."
Jersey's External Relations Minister Senator Ian Gorst has defended the island's new system - saying some French vessels have not provided the correct documents to get their permits. Of 41 boats applying for fishing licences, all but 17 had provided the evidence.
He called it a 'misunderstanding that could be put right'.
The UK's environment and food secretary George Eustice says Jersey is being reasonable.
"I think the threat that was made is completely disproportionate and unacceptable.
"We are working through the agreement, Jersey have already licensed over 40 vessels, they've been very pragmatic throughout this.
"They've also been clear that they'll process the remaining 17 or so as soon as they put forward the data, so I think it's unacceptable to make those sorts of comments."
Analysis: Sky's defence correspondent Alistair Bunkall says Downing Street is sending a strong message to France.
"Protecting UK fishing waters is one of the Royal Navy's oldest tasks, but Downing Street's decision to send two warships to the Channel Islands is a deliberate posture after France's initial threat to cut off electricity to the islands.
HMS Tamar and HMS Severn are OPVs - Offshore Patrol Vessels. Despite the rather lowkey name, they are sophisticated ships, especially Tamar which only entered service in 2020 and is equipped with the latest radar, sonar and weaponry technology.
The Royal Navy provides its ships to the UK government (Defra) for a set number of days each year to assist in patrols of waters around England, Wales and Northern Ireland. The devolved Scottish government has its own fleet.
The UK's Exclusive Economic Zone is the fifth largest in the world, extending 200 miles from the coast. The Royal Navy's role in UK waters is to prevent overfishing by foreign vessels and to enforce quotas. This has long been controversial but Brexit has made it more so.
Sending OPVs to Channel Island waters is, in itself, not controversial, but people I spoke to in the MoD and Royal Navy were not made aware of the announcement until late on. Fisheries post-Brexit were always going to be controversial, but it seems Downing Street is puffing out its chest and sending a strong message to Paris."