They say there are no secrets between sisters.
Except, perhaps, Japanese military intelligence.
Madeline Chidgey learnt this the hard way.
It was 1942 and the 20-year-old was fielding calls from her inquisitive younger sibling, Helen, about the nature of her new job.
But she couldn’t tell her much. In fact, she couldn’t tell her anything at all.
She couldn’t tell her little sister she spent her days holed up in the bustling garage of a Brisbane estate, translating and intercepting Japan’s strategic codes.
“She would write and say what are you doing up there all day? It just sounds as if you’re just doing letters,” the now 90-year-old remembers.
“She would say, `You don’t do anything, you just sit there and talk!'”
In reality, Mrs Chidgey was a member of what came to be a 4300-strong force of men and women dedicated to the top-secret task of deciphering vital intelligence signals.
The patient members of the Central Bureau worked tirelessly to pluck vital information about the enemy’s positions and tactics from radio traffic.
The initial headquarters were located in the Queensland capital, but eventually operations worked from the Philippines as the war in the Pacific intensified.
Their code-breaking efforts supported General Douglas MacArthur’s South West Pacific Area command, hacking into and interpreting Japanese air-communications to anticipate attacks.
Mobile units even used simple transmissions like weather broadcasts from major Japanese stations, such as Tokyo, Truk or Rabaul, to plot which Allied territories were likely to be bombed.
The work of these veterans, such as Mrs Chidgey, was honoured in Brisbane on Thursday with the unveiling of a new plaque to commemorate the site.
“I found it very satisfying knowing how important the work was,” she told AAP.
She’d joined the army two years earlier and was “tickled pink” to be one of the 20 people chosen to work at the headquarters.
Sometimes they’d be bundled into a truck just before midnight for the eight-hour night shift, making the trek to Ascot from the camp at Chermside.
Women, in particular, impressed with their capacity to crack codes and intercept signals, Intelligence and Security deputy secretary Steve Meekin said.
It was an intensely difficult task, given some Japanese intel was sent in a 71-character code at very high speeds – a challenge that meant workers had to invent their own, new system of shorthand to keep up.
But together, Mr Meekin said, the men and women of Central Bureau formed a “potent and very secret weapon” that helped boost the Allied forces’ chances of victory in the Pacific.
Unsurprisingly, a close bond was also forged amongst all those who fought on the signal frontline from that inconspicuous Brisbane garage.
They were wartime squatters of sorts, taking up space usually reserved for life’s luxuries, Mrs Chidgey joked.
“The garage would’ve no doubt had a Rolls Royce in it before us,” she quipped.
But once the war ended, she said the only high-value intelligence that passed through the group was good news – how everyone was, where they were, who they got married to.
It was a happy contrast to the necessity of wartime discretion and its unfortunate toll on family relations.
But, as the new plaque reads, that was the mantra of the Central Bureau: “Their Strength Lay In Silence”.