Mr Tan was arrested in 1963 under the Internal Security Act (ISA) for alleged pro-communist activities, and released in 1966. He was arrested again and detained for about three months in February 1977 under the ISA for allegedly joining a group to revive pro-communist activities here. Mr Tan always maintained he was not involved in Communist United Front activities.
He was most recently a contributor and editor of The May 13 Generation, a book of essays on the Chinese middle school student movement in the 1950s.
The following is a poem by Mr Tan about his time in detention.
What was it like ‘inside’?
A difficult question
Could you, would you really listen
Without sneer, to the end
How should I begin?
Should I start from the traumas of the raid
How liberty was so capriciously enchained
Without a warrant, without warning
On the dark hours
When even dogs slept undisturbed.
You were hauled into a world ran amok:
The mug shots, ‘turn out your pockets’
the thumb and fingers impressions
(Whatever for, I commit no crime!).
No one bothered,
The guard shoved you on,
Along the corridor of despair;
That first heavy thud of the iron door
Sealing you incommunicado from the world --
The wind, sun, moon, and the stars
And all that was human and dear
Should I recall the dark cell
At Central Police Station
A purgatory of perpetual night
The stone slab for the bed
Sullied, soiled mattress, no sheets
The pillow of tears and stains, no cover
Blood smeared walls, cries of past agonies
The rude, cruel hourly rip-rap of the shutters
“To check your health”,
So it was explained.
Should I narrate
The daily bath at the tap
The squat pan, dank and putrid
Meant to dehumanize, humiliate
Should we be thankful
For the daily ditch water
Which passed for tea
The stony crumbs for bread
The rice so callously tossed with dust
Should we be grateful
For the censored books and news,
To decontaminate our minds;
Should we be grateful too
For the unbearable heat
The lonely insomnia of the day and night,
Migraine and diarrhoeic fever
And panadol as panacea?
How could I ever forget those Neanderthals
Who roamed Whitley Holding Centre, 
Under cover of darkness,
Poured buckets of ice water
Over my stripped, shivering nakedness,
Slugged my struggling, painful agony
Circling , sneering, snarling
Over my freezing nudity,
More animals than men:
What induced this
Vengeful venom, violent score
To settle, not for a private grievance
But a public, democratic dissidence;
From whence sprang this barbarity?
What made men turn into beasts
In the dark, away from prying eyes,
Protected by a code of dishonour and lies
To ensure they survive and rise.
For sure, there were gentler souls
Who tried to be decent, no more:
The smiling guard who lightened the hours
With a chance remark, a joke
The barber who brought his scissors, cigarettes and news
The interrogator who handed a bible
Told him the elegant prose
Contrasted strangely with my current state,
How distant those beautiful thoughts were
From the violence to our liberty.
What then is the truth ?
A generation trapped in lies
Who rushed to defend, to justify
Never to listen, see or speak out.
Only when we open our hearts
Confront this barbarism
Can we truly exorcise our fears,
Finally emerge as a free people,
A liberated society.
 Formerly at South Bridge Road, now demolished, which had several cells frequently used for interrogation of police prisoners, from a month to a year, before they were dispatched to normal prison conditions at Changi Prison.
 A relatively new detention center built in the 1970s located off Whitley Road, used to hold political prisoners for short and medium term, mainly for interrogation .
The poem is published in Our Thoughts Are Free: Poems and Prose on Imprisonment and Exile, edited by Tan Jing Quee Teo Soh Lung Koh Kay Yew Ethos Books Singapore