Last week, the blog rolled away on autopilot without me. This is what I was actually doing…

I was secretly hoping that Helsinki would be cool in summer, but it’s as warm as London, if not warmer with all the extra daylight. Today there is not a cloud in the sky and the Finnish girls are wearing little shorts. Because I can, I decide to take a route past the statue of Gustaf Mannerheim. I am, after all, in town to look at his photo albums.

His predecessors, presidents Ståhlberg and Svinhufvud, are the elder statesmen who flank the steps up to the Finnish parliament. Their statues stare resolutely into the distance, as if busily ignoring everything around them. Mannerheim himself is mounted on horseback a little further down the road, as if taking point, in search of Russian intruders. His statue’s position is curiously mannered, as if a bunch of Finns whiled away long hours positioning him at a series of heated committees. He is neither approaching parliament nor walking away from it. Instead, he is walking his own path, along the street that now bears his name. These hot summer days, he is ringed at all times by an honour guard of boys on skateboards, who circle him watchfully and claim all the nearby benches as stunt ramps.

Today, for some reason, 200 Finns in suits are standing to attention on the steps of the parliament building opposite. Like Mannerheim’s statue, their positioning is also strangely mannered. Some unseen force has clearly compelled them to stand there, equidistant, unmoving. Suddenly, giant, unseen speakers erupt with a megawatt version of the teeny-bop anthem Heilutaan by the girl-band Tik-Tak. The suited Finns leap into an energetic, coordinated frug, whirling their attaché cases around and kicking their legs in the air until they are joined from either side by another hundred Finns, all inexplicably twirling orange and yellow umbrellas. Nervously, I look around for film cameras, but don’t see any. I scurry off to the National Board of Antiquities round the corner, and begin to wonder if I dreamt it. But I digress.

Between 1906 and 1908, Gustaf Mannerheim travelled right along the Silk Road from Kashgar to Beijing, and then on to Japan. All the while, he posed as a Swedish ethnographer, even though he was secretly drawing maps and taking data for the Russian army, just in case a war ever kicked off in Central Asia. For the first part of his trip, he was an unwelcome guest among a party of French explorers, led by the flamboyant linguist Paul Pelliot. Pelliot and Mannerheim couldn’t stand each other, which didn’t help, and they soon parted company, leaving Mannerheim to cross Asia on his clandestine mission, and Pelliot to scratch around in the ruins of a lost desert civilisation.

In 1909, the damning report Mannerheim filed about Chinese military preparedness was sufficient to convince the Tsar that China wouldn’t be a problem. Mannerheim’s notes on Asia were filed away and largely forgotten.

He was rewarded for his many months away from home with a promotion and a regiment in Poland to command, and that was the end of it. Mannerheim is famous because of something else… at some point in his life, his native Finland stopped being part of the Russian empire and started being, well… Finland. He led the forces of White Finland against the Reds in the Finnish civil war; becoming the new nation’s regent at a time of crisis; leading the country against the impossible odds of a Soviet invasion during WW2, and ultimately becoming the country’s president. That’s how I heard of him. My book on Mannerheim, four years in the making, is finally coming out in November 2009. It details his time in the Russo-Japanese War, his spying mission in China, and throws in his wildly adventurous later life as a bonus extra. There are, after all, few world leaders who have also run a coffee shop, taught the Dalai Lama how to use a gun, and ended up as the subject of a malicious puppet show. In a first for me, the first foreign-language edition of the book will actually be appearing a couple of weeks before the English “original”, as the Finnish publishers WSOY were so keen to get the book that they insisted on translating it before the English edition was sent to the printers. So technically, I suppose the Finnish version will be the “original”. A man called Jyri is translating it at the moment, and wishing he was in a summer cottage by a lake.

At the archives there are eleven file boxes waiting for me, containing a total of 1213 individual photographs, tagged and numbered. Some have been identified with names and dates. Others are vaguer – pictures of forgotten temples and obscure figures along the Gobi desert roads that the locals called the Sea of Death. Marja-Leena from the picture archives has stacked them all neatly for me, along with a final box of bonus images from other periods in Mannerheim’s life. Excitedly, I find a picture from the 1920s of a party at Mannerheim’s seaside residence in SW Finland, the House of the Four Winds. The girls are all dressed in Chinese clothes and clutching bamboo parasols. Finland was supposedly in the midst of Prohibition, but everyone seems merrily sozzled. Mannerheim smiles contentedly on the steps beside his half-sister Marguerite “Kissi”, while in the middle of the group, the face of a visiting Dutch prince is invisible beneath a straw boater.

But it’s the pictures of the ride across Asia that I am really here for, and they don’t disappoint. There are faceless Buddhist statues and intricate grottoes, dilapidated mosques and mountain vistas. A picture of a family of grubby Central Asian nomads includes their tiny daughter, mounted proudly on a toy horse – I know Mannerheim well enough to know that it was her, not her family, that was the true subject of his picture. There is an unexpected treasure in a picture of two white men sitting with a woman I know to be the Queen of the Alai. The men in the picture have sat unidentified for a hundred years, because one of them was written out of the record until 2007 and the other is in disguise. I recognise the former as Paul Pelliot, unmentioned in all 20th century editions of Mannerheim’s Asian diary, and only recently restored to the story. The other man is Mannerheim himself, his distinctive moustache shaved off at the beginning of his long trip, his usually-dapper hair shorn in a crew-cut against the Central Asian summer.

Here, there is a picture of a group of mandarins who came to pay their respects to Mannerheim on his travels: their robes are all creased in squares, as if taken out of the box for the first time. Here, there is Mannerheim shivering in a greatcoat at a viceroy’s banquet. Here, there is Mannerheim’s first sight of the western end of the Great Wall of China, taken in such a state of excitement that he has not even bothered to dismount. The ears of Philip the horse can clearly be seen jutting out at the bottom of the frame.

“That one has to go in,” says Harry from my publishers. “See if you can get us one of Mannerheim with a dead tiger as well.”

I can’t possibly take them all, but I take as many as I can. Marja-Leena seems a little surprised that I have picked out so many pictures.

“Will you really need them all?” she asks, totting up the price.

“Oh yes,” I say. “And can you throw in the one of the woman being attacked by a mutant bird.”

I mean “The Attack”, a famous allegorical painting of the Maid of Finland struggling to free herself from the clutches of Tsarist Russia, in the form of a two-headed eagle that is trying to steal the giant book of law that she is carrying. Marja-Leena has several versions, but says she has dug up the best one for me. While I’m at it, I choose a sweet little silhouette of Mannerheim from the 1920s which I think will make a nice end piece, or frontispiece… or something.

Next week I am coming back to Helsinki to poke around the military museum’s archives, just in case they have anything of Mannerheim’s war career I can use. I shall come via the parliament building, just in case there are 200 Finns doing the Macarena on the steps.