The Marine Accident Investigation Branch have published a report on a 2018 near miss between a Royal Navy submarine and a passenger ferry.

The near miss between a Stena passenger ferry and a Vanguard class submarine occured in 2018.

It should be noted that while Vanguard class submarines carry Trident nuclear missiles, the submarine involved was undertaking pre deployment training and was likely not armed with nuclear weapons.

At 1256 on the 6th of November 2018, Stena Superfast VII’s officer of the watch took urgent action to avoid a Vanguard class nuclear submarine after its periscope had been spotted close ahead of the ferry.

The report states that post-event analysis showed that, prior to the ferry’s course alteration, there had been a serious risk of collision. This near miss happened because the submarine’s control room team had underestimated the ferry’s speed and overestimated its range, resulting in an unsafe situation developing. However, the submarine’s control room electronic tactical display presented a picture of a safer situation than reality; this meant that safety-critical decisions made on board the submarine may have appeared rational at the time.

The MAIB say that the Royal Navy has taken a series of actions in response to this and similar previous accidents.

“As a result, a safety recommendation (2020/124) has been made to the Royal Navy to undertake an independent review to ensure that the actions taken have been effective in reducing the risk of further collision.”

Statement from the Chief Inspector of Marine Accidents

“On 6 November 2018, the lookout on board the ferry Stena Superfast VII spotted a submarine’s periscope close ahead. The officer of the watch then took immediate and effective action, turning the ferry to avoid a genuine risk of collision with a submerged submarine. The incident happened because the submarine’s control room team had underestimated the ferry’s speed and overestimated its range, resulting in safety-critical decisions being made based on inaccurate information.

Although there was no collision, this was the third accident or incident between a dived Royal Navy submarine and a surface vessel in 4 years, which is a matter of significant concern. The Royal Navy co-operated with the MAIB’s investigation into this near miss and has taken a series of actions, intended to prevent recurrence, in response to this, and the other similar incidents. However, I have today recommended that the Royal Navy undertakes an independent review of the actions that have been taken, in order to ensure that the risk of similar collisions has been reduced to as low as possible.”

You can read MAIB investigation report ’13-2020: Stena Superfast VII and Royal Navy submarine’ by clicking here.

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If the RN cant navigate in their own backyard, then we really are in trouble.

Robert Blay

Are you seriously questioning the abilities of a RN Vanguard class crew?


Cause there’s never been other incidents? Like smacking into a French SSBN for example?


Firstly let me say I’m a big RN fan. Secondly are you seriously suggesting this is a non-incedent? Crossing sea lanes under known shipping routes and times. Whether crew, system or protocol surely this is not right and not for the first time. As far as I’m aware nobody has confirmed it was a Vanguard.

Robert Blay

Of course I’m not saying it’s not a incident , but your rather dramatic claim the somehow the RN can’t navigate, and that we are all doomed is somewhat over the top. Nobody has the true facts. So let’s not speculate false claims.


Obviously you have a personal or sentimental interest in this, I not going over the top and I’m not saying/claiming we are all doomed, but from my perspective it doesn’t put us in the best light.

Robert Blay

Incidents happen, and happen to most other countries Armed Forces at sometime or another, just look at the recent fire on board the USN vessel. It doesn’t put us in a bad light, Incidents are few and far between.


If you say so, but I bet they are loving it over at RTNews.

Robert Blay

?‍♂️ maybe if something had actually hit anything, but it didn’t.


They missed each other by a matter of meters and mainly because the Ferry manouvered to avoid the sub. So it was more down to luck on the submariners part and should be classed as a major incident. Obviously they are not going to release how regularly they monitored the position of the fair but you would like to think it would have been multiples times during those 7 mins to ensure their calculations where correct but looks like that wasn’t done.

Paul T

HMS Ambush wasn’t so lucky – perhaps there is an inherent problem with the Periscopes the Royal Navy uses comment image

Andy P

Paul T, its not the masts, they work (or at least worked) fine. Its practice that is at fault here.

Andy P

The Bonhomme Richard would have been in dockyard hands so not the responsibility of the navy (at least that’s how it works in the UK).

Sorry, this was a BAD ‘near miss’, it shouldn’t have happened in known waters, they even carry the ferry timetables.

Steve P

Impressive from the lookout on the ferry!!


The Navy should employ him go their subs clearly.


Every vessel is supposed to keep a lookout even if they have the latest techie kit – this is kinda why. I used to be a watch leader (holiday role) on the sail training ship Lord Nelson and another one of the things we were warned to look out for was floating ISO containers which are often a bit like icebergs, mostly below the surface. So being a lookout is still a serious role on board, although there were stories of merchant ships sometimes being less than observant… First time I have seen a picture of the RN’s electronic periscope… Read more »


I can remember crossing the channel in the late 70’s the Regt was on board a civilian ferry overnight, we sent one of the new lads on deck for a 2hr iceberg watch.

Sceptical Richard

Wait, what?! How can this happen? Somebody’s career in that submarine needs to come to an abrupt end! Or maybe more than one person? Procedures need to change as well! We’re truly in big trouble if our submariners can’t navigate close to the surface in congested waters or near shipping lanes.


Actually, calculating range using only sonar isn’t easy and takes time to resolve. There is guess work involved in the initial ranging and sonar ain’t that good near the surface either, so huge potential for exciting moments like this one.

Having said all of that I would agree that the RN needs sort something out as 3 incidents in 4 years is asking for something tragic to happen.

Cheers CR


Hi Richard,

Just looked up the Stena Superfast vii, the ferry involved in the incident. It is a diesel ferry capable of just over 30knots! So a seriously and very unusually fast ferry, so I would guess there in lies the trap the Submariners fell into!

Cheers CR

Sceptical Richard

Hi CR. I’ve been on a super fast ferry from Bari in Italy to Patras in Greece. That one got up to 35knots! Amazing ship. Diesel powered as well. I can imagine that a diesel ferry with no sound deadening doing 30 knots must sound like a high speed train on the submarine’s sonar, not to mention the Doppler shift at that speed as well! Something very very wrong with the watchkeeping team in the sub that day! Besides, if in doubt, stick a periscope up. From the picture it looks as if they were at periscope depth anyway, and… Read more »


Hi Richard,
The problem lies in inaccurate early range estimates from a trainee Nav on the periscope being fed into the computer, when the Nav Officer took over he also overestimated (by less admittedly), the SMCS can calculate bearing changes combined with intensity changes to give a very estimate range but the system prioritises lookout info if at periscope depth or surfaced so compounded the error. More damning is the fact nobody seems to have looked at the camera feed and realised.
Ive read a fair few MAIB reports before but this report is actually quite interesting.

Sceptical Richard

Laser range finder?


While she’s one of the last of the superfasts on the Irish Sea (stena having retired most of them due to costs), ferries of this type and speed have been operating in the Irish Sea for around 20 years off the top of my head from both Belfast and Dublin. Seems a bit strange that a RN sub crew would be unaware of the speeds these ships maintain imo.

Glass Half Full

Something I was taught early in my career – Don’t assume!

Robert Blay

I do hope you are kidding right?


The ferry travels that route day after day, in the submarines back yard no less. Surprise can hardly be a factor?
Is the any chance the ferry picked up the periscope on radar? Pretty keen eyes to spot it otherwise!

Andy P

Just my view but in my experience they push through the Warfare officers far too quickly on submarines, its almost like a conveyor belt to get them through the jobs and progress. I could understand it if we were expanding the S/M fleet so looking to build extra numbers but that’s hardly the case. Being cynical, the good ones get a drive and then don’t want to get another one, there’s a lot that can go wrong so impact your career, and when you get to 3 rings, for the vast majority it seems that its all about their careers.… Read more »


Hard to find good help these days in the Navy I guess.


Supposing the sub was in foreign waters and that was a local vessel rather than a regular ferry crossing coming at it with intent?


Why would a Vanguard class sub be 2m below the surface in foreign waters?


Not sure if it was Foreign waters-the larger portion of the Irish sea on the two main ferry routes is in UK waters, but surely extra care is needed in such a busy shipping lane?


Sorry-I had not read DaveNBC

Harry Bulpit

Would love to see the face of the poor sod manning the periscope. Turning around to see a ferry on top of them. I know I would have need a underwear change.


You could not write this as fiction!


Never a good thing when one of your SSBNs is seen or detected. I’d hate to be the CO of that sub right now.

Mr Me

Stevie Wonder must have been manning the periscope! Seriously though, I would have expected the sheer volume of the ferry’s sonar signature would have suggested it’s too damn close for comfort setting more than a few mental alarm bells ringing! More than one of that crew will be finding their career progression coming to a grinding halt I would expect.

Levi Goldsteinberg

A hair’s width away from being a total catastrophe.


It’s because of a fundamental design flaw on our boats- no windows…