Mavis Lever was born on 5 May 1921 in Dulwich (UK) and was brought up
in Norbury and Croydon, where she went to the Coloma Convent Girls' School.
At the outbreak of WWII, she was studying German at University College
In 1940 she was recruited as a codebreaker by the
Government Code & Cypher School (GC&CS).
Initially she worked in London, where she worked on commercial codes.
She also had to check the personal columns of The Times for codes spy
messages. After showing promise, she was selected to work for
a research unit run by Dillwyn (Dilly) Knox at
Bletchley Park (BP).
Just 19 years old, she arrived at Bletchley Park (BP),
where she was introduced to Knox. Shortly afterwards, in March 1941,
she had her first success when she broke the Italian Naval Enigma again,
something that would prove to be vital to the victory in the
Battle of Cape Matapan.
Her most important work however, was the involvement in breaking
the Enigma G,
a special version of the Enigma that was used by the
German Abwehr and that was thought to be unbreakable.
Mavis met her future husband Keith Batey
whilst working at Bletchley Park.
The two got married during the war.
On 12 November 2013, Mavis died at the age of 92 after a long and
interesting life. Her Husband Keith, with whom
she had three children,
died in 2010 at the age of 91.
had been breaking the commercial Enigma
as early as 1937,
and in 1939 he was one of the driving forces behind the establishment
of Bletchley Park.
By the time Mavis arrived at the park, the codebreakers
in Hut 6 were already reading the German Army and Air Force ciphers.
Once Hut 6 was up and running, Knox had set up a research unit in
a small building at the stableyard next to The Mansion,
where he worked on codes and ciphers that had not yet been broken
by the people in Hut 6.
Arriving at the cottage at the age of 19,
Mavis was first introduced to Knox who,
eccentric and absent-minded as he was, said: Oh, hello, we're
breaking machines, have you got a pencil?
And that was it. She was never really told what to do and had to work
out the rest for herself from scratch.
That was the way the cottage worked.
Her first job was to work on the updated Italian Naval Enigma,
a system that had previously been broken by
Dilly Knox, but that
had since become unreadable. In March 1941 she broke into the system, after
a German operator had made a crucial mistake when sending a test message.
When Mavis picked up the test message, she noticed that there wasn't a single
'L' in it. Knowing that one of the weaknesses of the Enigma
was that a letter could never be encoded into itself, she
concluded that the operator had repeatedly been pressing
the rightmost key on the bottom row.
After reconstructing the wiring of the machine a short message
was received and deciphered.
It read: Today's the day minus three.
Not knowing what it meant, the team worked and waited for three
full days and nights until an extremely long and detailed
Italian Naval message came in.
The Battle of Cape Matapan
Apparently, the Italians were sending detailed messages about
a planned attack on a Royal Navy convoy carrying supplies from
Cairo to Greece. There were full details about the number of ships
and submarines that were involved, plus a full timing schedule.
The plans were sent on to the Admiralty in London, who passed
it on to Admiral Cunningham, the commander of the Royal Navy
who was responsible for the Mediterranean Fleet.
And Cunningham was able to play a nice trick.
During WWII, Japan was one of Germany's closest allies.
The movements of the Royal Navy in the Mediterranean waters were closely
watched by the Japanese consul in Alexandra (Greece) who was sending
detailed reports to the Germans.
Admiral Cunningham, who was also stationed in Alexandra, knew that
the consul was a keen golf player, so he took his clubs and an
overnight bag and visited the clubhouse, pretending that he knew nothing
and was going to stay for the weekend. Under the cover of night however,
he left the clubhouse and guided the nightly attack.
The rest is history. The Italians had no radar and were caught
completely by surprise. In a series of battles on 27/28 March 1941,
that became known as the Battle of Cape Matapan,
Cunningham attacked the Italian vessels, sinking three heavy cruisers,
two destroyers, and killing 3000 men.
Cunningham later visited Bletchley Park
personally to express his gratitude.
On this occasion, the girls had to rush out into a local pub to get some
wine to celebrate the visit of the Admiral and the victory at Matapan.
The Italians never confronted the Mediterranean Fleet
again and the Battle of Cape Matapan remained the last fleet action to
have been fought by the Royal Navy during the course of the war.
In 1943, Cunningham took the surrender of the Italian Navy.
Although her contribution to the victory in the Battle of Matapan
was truely significant, Mavis' most important work had yet to come.
It was her collaboration with Dilly Knox and Margret Rock,
another leading female codebreaker, on breaking the
a special version of the Enigma machine
that was used by the German secret service, the Abwehr.
It had not been broken by Hut 6 and for a while was thought to be unbreakable.
By now, the name of Dilly Knox' the research unit was changed to ISK, which
was short for Intelligence Services Knox,
or Illicit Services Knox.
During WWII, the Germans had spies in a number of capitals,
including London. After MI5 and MI6 had captured most of the spies
in Britain and in the neutral capitals of Madrid and Lisbon, they
sucessfully turned them and used them
to feed false information to the Germans. This operation became
known as the Double-Cross system (XX).
They had no idea whether the Germans believed the false intelligence
that was fed to them, and there was no way of checking this, as the
the device was so complex that the mathematicians in
Hut 6 had so far been unable to break it.
The Enigma G
had no Steckerbrett but featured 11, 15 and 17
turnover notches on the wheels, and had a moving reflector.
It was also known as the 11-15-17 machine.
Knox took over the job of breaking the Enigma G from Hut 6
and used Mavis Batey and Margret Rock as his assistents.
It was their job to test every possibility. On 8 December 1941,
Mavis broke a message from the Abwehr link between Belgrade and
Madrid, which allowed them to reconstruct one of the wheels.
Within a few days, Knox had broken into the Abwehr
Enigma. Shortly afterwards, Mavis broke another Abwehr machine,
the so-called GGG. This allowed them to read the high-level
Abwehr messages that confirmed that the Germans had bought the false
Double-Cross intelligence. The Double-Cross Committee
(XX Committee) 
was now able to feed the Germans small
pieces of information that led them to believe that the main
Allied invasion would take place on the Pas de Calais rather than
on Normandy. As a result, they kept two armoured divisions in the Calais
Mavis met her future husband at Bletchley Park and married him
during the war. One night, she was working alone on an evening
shift in the Cottage, when she was confronted with a difficult
codebreaking problem that she could not solve.
In order to solve the problem, Mavis turned to the mathematicians
of Hut 6, where break-in expert Keith Batey
was on duty that night.
Life at Bletchley Park was compartimented, and people
had instructions not to contact members
from other huts and not to discuss work outside the office.
Nevertheless Dilly had no problem in seeking contact with other
departments in order to solve problems. In fact, he stronly
denounced the military imposed need-to-know policy.
In the event, Mavis and Keith investigated the problem and
after several cups of ersatz coffee, he helped here solve the problem.
It was the start of a romance that would last for 70 years.
When she told him, Dilly had absolutely no objections with her seeking
help from Hut 6 and when she later told him that she was going to marry,
what he called 'one of the clever Cambridge mathematicians from Hut 6',
he even bought the young couple a lovely wedding present.
After the war, Mavis developed in interest in the protection of
historical gardens and successfully campaigned for the Protection
of Rural England, English Heritage and the Garden History Society.
In addition, she wrote many books abouts landscapes and gardens,
such as Jane Austen and the English Landscape (1996) and
Alexander Pope: Poetry and Landscape (1999).
The work at Bletchley Park was classified.
For more than 30 years she and her husband
Keith never spoke about
their wartime work, but after the revelations in
Frederick Winterbotham's book
The Ultra Secret she became
a frequent guest in television documentaries and newspaper
In 2009, she finally wrote a book about her wartime boss
and the work they carried out in the Cottage. The book was presented at a
special Enigma Reunion
that was held on 5 and 6 September 2009
at BP to commemorate the 70th anniversary of the WWII codebreaking centre.
The book is titled: Dilly, The Man Who Broke Enigmas 
and is a warm affectionate biography of one of the most intriguing
heros of World War II. During the book presentation at the Enigma Reunion,
staged in the library of the Mansion,
some books were even signed personally by Mavis.
The image above was taken on 5 September 2009 during the Enigma Reunion
at Bletchley Park. It shows Mavis and her husband Keith right at the centre
of attention in a private moment with David Hamer (left) and Sir Francis
Richards (second from the left). Despite their high age, both Mavis and Keith
were still in good health during this event.
Keith would die a year later at the high age of 91.
After an interesting life, Mavis died on 12 November 2013 at the age of 92.
1996Jane Austen and the English Landscape
1999Alexander Pope: Poetry and Landscape
2008From Bletchley with Love
2009Dilly, The Man Who Broke Enigmas (biography)
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© Crypto Museum. Created: Wednesday 29 January 2014. Last changed: Monday, 24 February 2020 - 00:27 CET.