Whatever their formal genre - travelogue, history, religious instruction, doleful memoir or Marxist ruminations - all of those books are really escapism. Writing provided not a literal way out of prison but an escape-valve in the form of mental exercise, self-discipline and projection. The same rule of enforced, self-conscious distraction from confinement holds true even at the movies, whether with Burt Lancaster's birds at Alcatraz, Tom Hanks' basketball on a tropical island or Tim Robbins' endless digging in Shawshank prison.

All those unfortunates were trying to keep themselves sane. However grim their predicaments, none of them confronted as daunting and demoralising an imprisonment as Scott Heywood, captured by the Japanese and set to work on the Burma railway. Among Heywood's 13,000 fellow Australian POWs constructing the railway, 2650 died. All the survivors were subject to brutal violence, rigorous deprivation of rations and an incessantly severe work regime.

Their story has recently been revived by Richard Flanagan as a novel, The Long Road to the Deep North. Heywood's writings stand a long way from Flanagan on the literature continuum. His writing took the form of 389 imagined letters to his wife, scribbled on scrounged paper, hidden from Japanese guards.

We might well ask, with Elizabeth Barrett Browning, "how do I love thee? Let me count the ways". The melancholy answer, though, is that our language offers us only a few credible ways to tell a loved one how we feel. Although our emotional reserves may not drain away, our linguistic ones certainly will.

Two authors have chosen to exhume Heywood's letters. One, Peter Rees, is a journalist and military historian. The other, Sue Langford, is a psychologist. Their quite divergent skills and experience complement each other. The presence of a psychologist is first obvious when readers are taught that, during their first months' courting, lovers remain in "a state of limerence". The military historian announces himself by giving the specific names of eight units travelling in convoy.

The joint authors suggest that they have unearthed "an uplifting and optimistic treatise" on life and love. Their dedication is to a love "which endured the worst of times in anticipation of the best of times". As did Heywood, the authors might sometimes overdo the sentimentality in this tale. A battle arrives, for instance, "raw and vibrant, terrifying and full blast".

Off, then, Heywood goes to war, a 30-year-old married bloke with two kids, some rank (RSM), sporting prowess and a good singing voice. His background was as staid and conventional as were his foolishly disparaging remarks about "the yellow fellow".

As the story begins, Scott Heywood might appear an unlikely hero. Set for a career in a rural cordials factory, he joined the Army Reserves, then the regular forces, before the Second World War. Along the way his thighs were lacerated by a model aeroplane mascot on a car's radiator cap. In those pre-war days, Haywood actually comes across as a bit of a whinger, complaining about his illnesses, logistics, separation from his loved one and the mechanics of machine guns. Little did he know the genuine causes for complaint he would soon have to cope with.

Captured in Singapore, held in Changi, then transported to the Burma railway, taken off to Saigon, back to Singapore, and finally on to Yokohama, Heywood inhabited for four years most of the circles of Hell. Insults, disease, malnutrition, beatings, lack of medicines and hard labour were his enemies; "mateship was crucial". In this context, mateship seems to connote sticking up for fellow soldiers, not shirking, and trying to lift spirits among the prisoners.

Leaving aside his genuine affection for nature's world, Heywood was not a great prose stylist. Some letters may seem wooden or repetitive. Ironically, the narrative becomes intensely dramatic when Heywood is attacked by Americans rather than Japanese, first by submarines, then by bombers.

The authors speculate that writing letters might have induced "a stillness of mind", become "critical to his sense of equanimity" or "put him in the frame of mind to sleep". Perhaps all those hypotheses are true, along with the desperate will to survive characteristic among survivors of the Nazi concentration camps.