The Battle of Britain Five Months That Changed History, May—October 1940 by James Holland (z-lib.org).epub

But there was another considerable concern for Konteradmiral Fricke and
his team, and that was mines. A channel through enemy mines had to be
cleared, whilst at the same time protective minefields big enough to protect
German vessels from the British navy needed to be laid either side of this
channel. The problem was that as soon as mines were swept, new ones were
laid, and as soon as they were laid, the British swept them. Not completely,
of course, but the Kriegsmarine would never be able to guarantee a passage
free of mines or sufficient protection on its flanks. ‘This fact,’ wrote Fricke,
‘must receive the greatest attention.’
Slipping quietly out of Immingham on the Humber at dusk on 1 August
were seven British minelayers, heading for the East Coast Mine Barrier.
Amongst them was HMS Icarus, armed with twenty-six Mk XVII and XX
antenna mines. A deep and extensive minefield had already been laid
around most of Britain, although through the Dover Straits and along the
east coast the mines were particularly extensive. The idea was that they
were far enough out to give any east-coast convoy a protective shield. They
were obviously of no use at all against aircraft, and of limited use against
highly manoeuvrable S-boats, but against other enemy shipping – not least
barges – they posed a serious threat.
Icarus had been repaired and had been back out at sea by the third week
in June, and since then had been carrying out a combination of minelaying
duties and invasion patrols. One night in early July it had been suddenly
ordered to hurry to Dover with all urgency. ‘We went hell for leather that
night,’ says Andrew Begg, who was still one of the ship’s engine room
artificers, ‘and it was a black night.’ The rumour going round the ship was
that the invasion had started, but when she reached Dover at dawn, there
was nothing going on at all, so she headed back to Immingham. ‘We never
found out what that panic was about,’ says Andrew, ‘even our skipper never
told us.’
Having sailed through gaps in the minefield, the convoy now headed
down the eastern side of the barrier until it was off the east coast of Norfolk.
At around 10 a.m. on the 2nd, the minelaying operation began, each vessel
heading in a steady straight line and dropping mines off the back of the
ship. Each mine plunged to the bottom of the sea, where its weight, or
‘sinker’, moored it to the seabed and then the mine floated to the top, where
in this case it was set to sit at a depth of around twelve feet. Others were set