Does the world need another book about TE Lawrence? And do I need spend a couple of years of my life writing one? These were the questions I had to answer before deciding to start on Young Lawrence. As a writer on the Kuwaiti newspaper Al Jarida pointed out in his recent review, in 1935, at the time of Lawrence's death following a motorbike accident, the British Library held eight books about his life and achievements. They now hold 108. Make that 109, as they should also have a copy of Young Lawrence by now because Reader, I wrote it.

I had been thinking about it for a long time – since 1989, to be precise. That was the year I first meandered through the Syrian mountains between Damascus and Aleppo and saw some of the spectacular Crusader castles. That was also when I first came across Lawrence's Crusader Castles, a reworking of his Oxford University thesis with his sketches and photographs of the castles as they were when he first saw them in 1909.

I was curious about that first journey he made to the Middle East. He was 20 years old and at the end of his second year studying medieval history. He was also tough, choosing to walk alone from Beirut through what is now Lebanon and Israel to the south side of the Sea of Galilee and then back up to Beirut, on to Aleppo and into what is now Turkey.

He was travelling in summer, when temperatures get up into the 40Cs, in hobnail boots and a bespoke suit (plenty of pockets to store papers and money), a small bag with a camera, a change of clothes and a pistol. He had ignored the advice of Charles Doughty, an expert on travel in Arabia who had told him that the journey would be “wearisome, hazardous to health and even disappointing”. Lawrence went, found it wearisome and hazardous to health (he caught malaria and was badly beaten in a mugging) and loved it.

Who wouldn’t be intrigued? But discovering that he was arrogant and foolish wasn’t why I wrote the book.

A few years ago I was walking in Damascus with a friend who was born in the city. Each time I visited, he had taken me out at night, sometimes to eat – once, memorably, into a dingy cafe that served large bowls of sheep’s head soup – and other times to a cafe, usually to join a group of writers and film-makers, and sometimes just to walk. It was on one of these walks that he told me why the city “worked”, why its different religious and ethnic groups were able to live together. He thought it was to do with the city’s architecture and its traditions. But I pointed out that in Lawrence’s time, under Turkish rule, there was plenty of cohabitation, and not just in Damascus: the eastern part of the Ottoman Empire was as mixed as London is now.

When the Arab spring of 2011 withered and the fighting started, there was talk of apocalypse and that led me back to Lawrence. What was he doing before the first World War broke out? In the summer of 1914, he was an archaeologist on a British Museum dig on what is now the border between Turkey and Syria. The site was a Hittite city called Carchemish, a huge mound on the banks of the Euphrates River.

Lawrence had been working there since 1910, first with the Keeper of Oxford’s Ashmolean Museum and then Leonard Woolley, among others. Later, after his death, Lawrence’s younger brother Arnold wrote that this was the time when TE was happiest, something echoed in a letter he wrote from Carchemish late in 1913: “I have got to like this place very much: and the people here – five or six of them – and the whole manner of living pleases me.” He was planning on staying. After the Carchemish dig, he thought he might travel with a tribe in Arabia and then dig somewhere else.

Lawrence returned to Britain at the end of June 1914. He thought he would be away for six weeks or maybe a little more and then would go back to the Euphrates, where he had left most of his belongings, including his pistol. He was carrying notes from a journey he had made in the Sinai desert a few months earlier, a sketch of Dahoum, a young Arab who had become his protégé and constant companion, and the finished manuscript of a book he had written about his adventures in the Middle East. The manuscript was called Seven Pillars of Wisdom. The day after Lawrence reached his family home in Oxford, on June 28th, 1914, the Archduke Franz Ferdinand was assassinated in Sarajevo and exactly a month later the war began. A month after that, Lawrence burned the only copy of Seven Pillars.

Why did he do this? After the war, when he gave that title to another book, he referred to the manuscript and said he burned it because it was immature.

I thought about that.

There was other writing – letters and journals – and they were equally immature, more so perhaps, and he didn’t burn them. So, perhaps there was another reason for burning it.

That is why I wrote Young Lawrence, to put some of the scraps of that manuscript back together. When he burned Seven Pillars in August 1914, before he went to London and on to the war, he assumed he would not return. By destroying the pages, he was tidying up his affairs, making sure that he left behind only what he wanted to be seen by his parents, particularly by his mother.

So what might have been in the manuscript that Lawrence did not want to survive him? That was what I wanted to know and yet none of those hundred and more books in the British Library had focussed on this – in the opinion of the most experienced of Lawrence biographers, this was the one part of his life that had been passed over, in the hurry to get to the war. And yet his part in the war – how he did what he did and, more poignant, why he did what he did – can only be understood by knowing about this earlier part of his life.

In the process of research, as I travelled from Turkey and Lebanon to Jordan and Egypt, from Gezi Park riots to Tahrir Square the day that President Morsi was toppled, I realised that Lawrence was also allowing me to see the region as it was before the victors carved it up along the lines agreed in the Sykes-Picot agreement. It then became clear why he was so opposed to the postwar settlement, why he wanted viable and independent Arab states, why the Middle East would have been a very different place today.

There were other reasons, but by this point it was obvious that I had an answer to my original question, a loud yes, there was room for another book about this extraordinary man…

Young Lawrence: a Portrait of the Legend as a Young Man by Anthony Sattin is published by John Murray (£25) © Anthony Sattin 2014