Saunders Roe (Anglesey) Ltd

Britain's First All Aluminium Alloy MTB 539

Prototype Motor Torpedo Boat MTB 539  (P1602)

Hot News: An attempt to find and dive the MTB was made 13th July 2013. On the day she was not found.

Scroll to the bottom for photos of the dive team

A new talk is available on this historic boat. See Illustrated Talks page HERE

4th October 2013. New photo (below) found in France.

HMS P1602 1951 

The company lay on the shores of the Menai Strait between the Isle of Anglesey and Caernarfonshire (now Gwynedd) during WW2. Originally the company was known as Saunders Engineering and Shipyard, or SEAS. It was here that Catalina flying boats were flown in from Canada for conversion to RAF requirements. The work was done here rather than in Canada as updates were constantly being made to the specifications so it was therefore more convenient to do the work in the UK.

After the end of WW2 the company turned to building Naval craft in the form of Motor Torpedo Boats - MTB's and Fast Patrol Boats - FPB's.

The very first of the SEAS MTB's was a prototype for the Royal Navy's First  all aluminium hulled craft of 75ft overall length (72ft waterline) It was designed and built at the factory located at Fryars Bay, one mile east of Beaumaris.

My father Victor Percival Mills was new to the drawing office and  carried out a lot of design and drawing work for the boat. It is only recently that I discovered this information from John Stops who worked at the factory in the early 1950's. John told me the boat was code named 539 at the works, but was later re-named P1602 by the Navy when it went into service.

It was fitted with three 1,500 bhp American Packard petrol engines (see the notes before the engine room photos).

I was informed that P1602 developed hydraulic failure to one of the Rotol variable pitch propellers that threw one propeller into reverse pitch while operating at full speed. This had the effect of reversing the drive on one side that threw the boat so violently to one side that crew were scattered across the deck. I heard that the Saunders Roe boatman Harold Jones suffered a head injury that he carried for the rest of his life to bear witness to the event. The sudden change in load to the transmission is thought to have wrecked the Rotol Vee drive gearbox that could only be repaired back at Anglesey. The engine and gearbox were thought to have been removed for inspection while on the south coast of England, but as they were not repairable when the extent of damage was found were only loosely replaced . As a tug was heading north (possibly to Liverpool) P1602 took a tow to save further mechanical damage. When only a few miles from Fryars Bay it ran into a storm and the loose engine shook off its mountings and punched a hole through the aluminium hull. The boat immediately sunk, fortunately without loss of life. The wreck is still said to be lying off the east coast of Anglesey in around 40m of water. When last seen by divers it was sitting flat on the sandy bottom with fairly light damage apart from a wrinkle in the aluminium hull on one side and a damaged bridge ans that the action of the tidal flow has polished the hull to a shiny finish. The engines have not been seen as their hatches are presumed to be intact and still closed. It would be a challenge to anyone to raise Briatain's First all aluminium MTB and the first of the SARO fleet. Any takers?.

As my father was so involved with the design in 1945, a couple of years before I was born, I have recently become very interested in its history.

I am delighted to have recently discover a collection of photographs that have been digitised and somewhat 'cleaned' up, and a bundle of detailed drawings. A small sample of drawings are at the bottom of this page.

You will notice it numbered 539, P1602 and sometimes without any number depending on the date it was photographed.


If you wish to contact me please- 


539 ready for launching. Note the use of old aircraft wheels on the launching trolley. 


539 on the move


539 being rolled bow first towards the slipway.


539 being cautiously eased around the corner of the drawing office. Shop 1 is to the left and Shop 2 to its right.


539 almost at the slipway. The lifeboat station can be seen just above the port torpedo tube.


539 on the original slipway that served the flying boats.


539 being eased into the sea at Fryars Bay. Snowdonia in the background. 


539 successfully launched with proud workforce giving a rousing cheer.


539 at Friars Bay before the fury of those three Packard engines broke the silence of an early winter morning with 4,500 bhp.


A wonderfully dramatic view of her roaring east along the Menai Strait with Snowdonia in the backbround. 


539 on trials with Penmon in the background 


Closer view of 539 


P1602 making waves


P1602 on a charge with its triple Packard petrol engines


539 now renamed P1602 


P1602 ticking over.


P1602 outside the Saunders Roe factory at Cowes, Isle of Wight.


 P1602 at anchor on the Menai Strait.


Closer view.


P1602 on the Menai Strait off Glyn Garth 


P1602 on the Menai Strait off Glyn Garth (Anglesey) with Bangor beyond her stern and Beaumaris off her bow.  


P1602. View looking northeast with Bangor Pier beyond stern. 


 P1602. View looking northeast with Bangor Pier beyond bow.


P1602 at HMS Hornet, Gosport with the 'Suicide Bridge' just behind her.  


P1602 mast, aerials and radar


P1602 view looking forward. 


P1602 looking forward to starboard 18 inch torpedo tubes.


P1602 looking aft from bows


P1602 closer view of bridge and torpedo tubes. Note the rocket flare launchers mounted on top of the forward 18" torpedo tubes. 


P1602 starboard torpedo tubes and steps to bridge


P1602 looking aft from bridge 


P1602 looking forward from beneath rear machine gun 


Port Aft Quarter showing Engine Room ventilator and CSA Unit (Chemical Smoke Apparatus) on the corner of the deck


P1602's Oerlikon 22mm Mk VIIA machine gun mounting.


P1602 at Saunders Roe with Friars Bay and Penmaenmawr mountain in the distance


P1602 posing with a pair of aluminium bodied LT buses. 


Port propeller showing missing rivet heads from cavitation.


Starbord propeller showing missing rivets from cavitation. 


P1602 triple propellers. Cavitation was a problem and many aluminium rivet heads were eroded away leaving that section of hull full of small holes.

It was one of these props that flipped into reverse or neutral at full speed that caused the transmission failure that required it to be send on its journey back to Anglesey and to a watery grave.


New ROTOL marine variable pitch propeller. Flyght magazine 29 July 1943 



P1602 visit to Liege. 



There have been rumours of Vosper Thorneycroft high octane petrol engines fitted to the boat, but now we have photographic evidence of the actual engines.

They were three American Packard 4M-2500 V12 Type W14 marine petrol engines each delivering 1500 bhp giving the boat a capability of approximately 42 knots. The drawings also refer to "3 Packard Marine Engines Type W14". These engines were developed from an original Packard design (M-2500) and not the Rolls Royce "Merlin" as often believed. The early development to that original design entailed certain modifications to the carburation, supercharging and crankcase design (similar to the Merlins) so these Packards became commonly known on this side of the 'pond' as Packard 'Merlins', hence the confusion. Packard engines were also fitted to the later Vosper built Gay Class MTBs produced before the SARO built Dark Class that used just two British Napier Deltic 18 cylinder Diesel engines in each boat.

The engines had their crankshaft outputs facing forwards then reversed through Rotol Vee- gearboxes to change the direction to the propeller shafts. The propellers were Rotol variable pitch type that enabled the boat to be reversed without a reversing gearbox. The pitch was controlled hydraulically and is believed to have 'defaulted' to reverse direction when no pressure was in the system. The photos also show them feathered to a horizontal or axial flow with the shaft direction. It was probably a sudden hydraulic failure to one prop that caused the sudden reversal or flat feathering of a prop that caused the catastrophic failure to one of the gearboxes.

Fuel consumption - Approx 500 Gallons of 100 octane petrol per hour.

common misconception is that Packard Merlin engines were used in American PT boats; the engine used was in fact a Packard V-12 engine, a modification of the Liberty L-12, totally unrelated to the Merlin. The possibility is that these engines were also used by British MTBs and MGBs.

(certainly in at least MTB 539)

Rolls Royce Merlin

Packard 4M-2500



To hear the triple Packard engines in an American PT Boat check out this:




539 / P1602 Engine room looking aft and clearly showing the forward central mounted Packard 4M-2500 type W14 petrol engine. The engines drove the propeller shafts through vee gearboxes.


539 / P1602 engine room 


539 / P1602 engine room 


539 / P1602 engine room control consul. This must have been an exhillerating, but utterly deafening place to work!


American Packard PT boat engine


Packard 4M-2500 PT boat engine



Above - Possible spark plugs for Packard engines - KLG RC/P

Below - Possible alerative plugs - KLG RM60/1





A small selection of the recently found drawings of MTB 539 (dated 1945-1947)




Below: The drawing shows "3 Packard Marine Engines Type W14





Perspective drawing by Victor P. Mills of the World's first all-aluminium MTB hull construction


Latest drawing find. Another drawing by Victor Mills dated 4th February 1946 showing two of the three Packard engines installed in MTB 539. The original pencil drawing was very badly marked and 'foxed' through age, but a run through Photoshop has cleaned it up considerably.


Below: Close up of engines.


Above: Oerlikon 20mm Mk VII A Twin mounting



 A 1951 advertisement promoting the aluminium work carried out by SARO

This erroneously claims to be the World's first alloy MTB. The Amrican PT-9 was of aluminium alloy and built 15 years earlier. There were also two steam powered aluminium torpedo boats for France in 1894 and Russian in 1895.


The Hunt Begins: 

13th July 2013. The first search for the MTB took place by divers in a 5.5m RIB with side scan sonar. There were two published location both of which didn't reveal the boat. I spent 8 hours with the divers as they firstly went down to the Kincorth and later roared off to search for the MTB. Another search, another day.

Thank you to everyone who came searching for MTB 539 (P1602)

Special thanks to Ian for inviting me to join the search.


     MTB 102 TRUST 


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