This was due to the 'Z' tank being improperly vented on diving. Lt. Cdr Mills had ordered W, 'Q' and 'Z' tanks to be flooded, but 'Z' tank was blown completely. TETRARCH assumed a twenty degree bow down angle which could not be checked by blowing her number 1 and number 2 main ballast tanks. She shot to the surface and remained up there for about half a minute before diving to 350 feet, where Lt. Cdr Mills managed to catch a 'perfect trim' laying sopped in the water neither sinking or rising by using 'Q' tanks.

TETRARCH was in fact, lying on a heavy layer of water, such as one frequently finds in the approaches to the Baltic, and it was this that in the end proved her salvation. The heavy layer was caused by a sub-surface current which was setting in the opposite direction to that above. Slowly the two were being carried further apart, the hunting trawlers in one direction, and the hunted TETRARCH in the other. There was nothing for it but to sit the attack out, so all machinery was stopped, except the forward hydroplanes motor. The depth charging continued, then the order was given to stop the forward hydroplanes motor. It appeared that it was this noise which was keeping the enemy in contact, for their 'HE' now grew fainter.

The men in the submarine lay silent, trying to conserve the little oxygen left in the boat. Low the deck, the batteries were getting weaker, the last of their power being slowly used up. There was no chance now of coming up to the surface and recharging their batteries, for the night was fast passing, and the foul air would have to remain, and get more foul, throughout the long hours of another day.

To add to the foul air was the sanitary buckets lined up in the gangways. Shortly before noon TETRARCH came up to periscope depth for a quick look around, the sea was empty, and it appeared that the hunters had given up. But there was still no chance of coming up to the surface, for TETRARCH was right in the track of the German air traffic to Norway, and to be sighted by an aircraft would inevitably mean the return of the A/S vessels. So remorselessly, TETRARCH went deep again, to use the last dregs of her battery power in a slow crawl towards safer waters.

That night at 2130 hours, the TETRARCH again came up and surfaced. She had been submerged apart from the two minutes on the surface the previous night, for 42 hours and 40 minutes. As she broke surface and opened her hatches, Lt. Cdr Mills and the lookouts searched the sea anxiously. There was nothing in sight, and the TETRARCH's ordeal was over.

Many of the crew were violently sick as the foul air was replaced. All were dizzy and mentally as well as physically exhausted. One man having to breathe oxygen via a DSEA (Davis Submarine Escape Apparatus) set for the last twelve hours of the dive. The crew recovered rapidly and TETRARCH was able to complete her patrol before returning to safety - much the same sort of experience came the way of HHS/M SEALION under the command of Lt. Cdr. Ben Bryant on its seventh war patrol. Lt. Cdr Bryant was later to make a name for himself when he commanded HMS/M SAFARI in the Mediterranean.

HSM/M TRUANT again left Rosyth Scotland on the 24th April, to carry out a special operation near Kristiansand Norway, when she ran into a new laid minefield in the Skagerrak. As her Skipper, Cdr. C.H. Hutchinson edged TRUANT through very carefully, there was suddenly a metallic clang forward. They listened in dead silence as a mine's mooring wire scraped along the outside of the hull. The wire seemed to be caught up for an instant on one of the propeller guards and then was thrown clear.

A few seconds later more wires rasped along the hull, the sound greatly magnified by the water - it was like being in a drum. For a submarine is itself a hydrophone, a receiver that vibrates to sound waves. Again, the wires seemed to clear the hull, when the boat was rocked by a loud explosion. A mine had hit the after end of the conning tower. Abandoning all further attempts at concealment, Cdr. Hutchinson brought TRUANT up to the surface and headed home at full speed. The crew worked with great effort to repair the damage and make TRUANT seaworthy.

It was a triumph of determination and courage on the part of both captain and crew, for the boat had been so severely damaged and she had been within sight of the enemy coast and their air and surface patrols. Finally they reached home safely.

An unfortunate accident occurred on the 29th April, causing the British to lose their eighth submarine of the war. But this time it was not due to enemy action. It happened off the east coast of England in ' the area known as the "wash ". This particular area was in the path of the east convoy route, running the length between the Tyne and the Thames; and nearly every night it was raided by German E-Boats on the lookout for action against any shipping. It was a miserable, foggy evening - the fog had rolled in leaving patches of fog banks and visibility was poor.

HMS/M UNITY was running on the surface, showing no lights and almost invisible to other ships even at close range, when suddenly out of the fog, showing no lights or blowing her fog-horn, came a merchant ship. There was no time for UNITY to dive before the merchant ship hit her. The ship's bow struck UNITY with a sickening metallic crash, some 20 or 30 feet abaft the port bow.

Water was collecting aft, making her stern heavy, so that she took up an angle of ten  degrees down by the stem, giving her a depth of 425 feet. To get her on an even keel, a bucket chain was formed in the boat and the after bilges bailed out by hand. The water was transferred forward from hand to hand until at last the stern was brought level with the bows. After several hours TRIDENT made her way clear of her attackers and was brought up to periscope depth to find the sea empty, and finished her patrol returning safely to her base at Rosyth on the 4th May.

Again, I have to emphasize that in a book of this length it is not possible to mention in detail the exploits of all British submarines individually. So it becomes necessary to generalize in some cases. Nevertheless, there are some episodes which must be described in detail.

On 4th May the old RIVER CLASS fleet submarine HHS/M SEVERN who had been a part of the thin red line from the beginning of the war off the shores of Norway, sank its first enemy vessel, the 1786 ton MONARK.

On the 5th May, the British lost their ninth submarine of the war. This time it was not sunk but captured by the enemy; much to the dismay of the British Admiralty who would rather it had been sunk, or scuttled by its crew than captured by the Germans. Unfortunately not much thought had been given to arrangements for destroying a boat in the event of being captured.

HMS/M SEAL commanded by Lt. Cdr. Rupert Lonsdale, had been laying a minefield southwest of Goteborg, outside territorial waters, in the narrow strait between Skagen, the tip of Denmark and Goteborg; the entrance to Kattegat, and the German port of Kiel, which was the home base for most of her fleet.

HMS/M SEAL had been previously spotted by German aircraft and chased by anti- submarine trawlers, dropping their depth charges periodically hoping to destroy SEAL or at least bring her up to the surface so they could finish her off by gunfire or by ramming her. This led, on the afternoon of 4th May, to being hunted and depth charged by German E-Boats.

In avoiding their attack SEAL passed through an unknown German minefield. It was only when they heard the scratching and scraping nowise moving along the boat's hull did they realize they were in a minefield, and it was a mine's mooring wire rubbing the boat's hull that caused the noise. The crew as full of anxiety, waiting for the mine to clear the boat. Then all of a sudden it was over, the scraping noise stopped, the danger had passed. Lt. cdr. Lonsdale ordered 'GROUP DOWN' so as to pass cautiously and slowly through the minefield.

Fifteen minutes had passed when the noise started again, that scratching noise as a mine's mooring cable was rubbing the boat's hull, the orders to stop the main motors was given. No matter what maneuvers Lt.Cdr. Lonsdale attempted, this time they could not break free from the mine's cable. There was no time for caution now, so he brought the boat up to periscope depth.

Raising the periscope, a quick glance to the bow and then up into the sky, he brought the lens toward the stern and depressed it slightly. There was no sign of wire or cable, but there bobbing close astern was a mine. It was covered in green slime, and could have been in the waters for some months. Somehow SEAL had severed the mine's mooring cable and it had caught around the after planes in a dangerous position as it could veer into the boat's propellers.

Controlling the boat had become difficult. Lt. Cdr. Lonsdale informed the crew that they were towing a mine about six feet astern of them, and he saw stunned expressions on their faces. Some of the crew, knowing the danger, were praying quietly to themselves, others just crossed their fingers, waiting for the C.O. to act, to perform a miracle and free them from the mine. SEAL could not surface so they could cut the mine adrift because of the numerous EBoats buzzing around, just waiting to attack the British submarine if she surfaced.

Some three hours later, still towing the mine and attended by EBoats, SEAL suffered a heavy explosion aft. The mine had exploded, which caused flooding and SEAL bottomed by the stem in 130 feet of water with a marked angle bow-up. Whether the E-Boats above had heard the explosion or not, thinking that the mines had finished off the submarine, they departed looking for other targets.

In SEAL, frantic efforts were being made to reduce the flooding and deal with the machinery damage. The after bilge pumps could not handle the flooding, so bucket brigades were formed, passing buckets of water forward to be poured into one of the forward auxiliary tanks, but the crew was rapidly becoming exhausted, suffering from a combination of carbon-dioxide poisoning and the lack of oxygen. SEAL had been submerged for over 30 hours. It was not until 1 a.m. the following morning, 5th May, due to the crew's superhuman effort in repairing most of the damaged machinery and controlling the flooding that Lt. Cdr. Lonsdale managed to bring SEAL to the surface.

The SEAL proved to be sluggish and uncontrollable, no matter what the C.O. and his crew tried to do to control the boat. So it was decided that an attempt would be made to steer SEAL stern-first into Swedish territorial waters, an effort frustrated by the early dawn. Proceeding astern was precarious and hazardous, as SEAL was in an aircraft patrolling zone and could be attacked at any moment.

About 3 a.m., SEAL was spotted and attacked by German aircraft. Not only was she bombed but strafed by their machine guns, only being able to return fire with ineffective Lewis machineguns, both of which soon jammed. Some of the crew were badly wounded, some killed, and the First Lieutenant was badly injured by the German strafing. Low flying German planes (now there was no return fire) saw the predicament SEAL was in, and the wounded crew laying on the casing, stopped their attack and just kept circling above them.