Saturday

Back to Shanghai to root around the archives once more. I'm here for three weeks' research on a British Academy exchange scheme with the Shanghai Academy of Social Sciences. First things first: buy a bike. The once-quiet streets of China's cities are jammed with taxis. As "contemporarisation" proceeds apace, the bike becomes more and more vital to getting around.

Next, take brand-new bike to a street-side repairman to have it finished. If it has just come from a Shanghai bike factory, it won't be ready yet. Ichoose an old man, opting for one who looks bewildered as I approach. I have him fiddle with everything, particularly the pedals, in a vain bid to prevent other repairmen stealing bits for use as spare parts.

Monday

First day at the archives - past the noticeboard counting down the days till the retrocession of Hong Kong; wry smiles all round as I re-enter the arena. This being my third visit I am officially lao pengyou (an old friend), and have a little more leeway than first-timers, but stonewalling is the predictable first response. Time to insinuate myself a little, perhaps even whine a bit; the things I do for history. Still, with any luck I won't have to get legless on Shaoxing wine again, as happened last time when the archive staff took me out for dinner (I got the files though). I'm writing a history of the British-dominated Shanghai Municipal Police, which patrolled the former International Settlement of Shanghai from 1854 until 1943. The papers of this force, and the council which controlled it, are lodged here. The first tranche of material has been officially released, but is being opened at an agonisingly slow pace. Still, things have improved since 1991, when I was given a cup of tea, a meeting - the conclusion of which was that I was officially and pleasantly classified as a "travelling scholar" - and then told to go home.

Wednesday

Shanghai leaves me speechless, literally, for the choking dust and cement from the building site that still purports to be a city plasters the inside of my throat as it plasters my hair and clothes. Up to the early 1990s, Shanghai was largely as it was when the Pacific War began in 1941. It was as if the European and American settlers and expatriates moved out overnight and the Shanghainese moved in. Now the destruction of European Shanghai progresses at a still-increasing pace. Where once the returning visitor lamented a missing 1930s apartment block, now the city bears the scars of missing neighbourhoods. Shanghai strives instead to thrust upwards gleaming towers of Hong Kong-styled glass and metal.

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Saturday

Shanghai cycling is a tricky business (even if you still have your pedals - and I had one of mine stolen on day two). First: buy a woman's bike, a cross bar makes rapid emergency dismounts awkward. Second: learn to ring the bell promiscuously, so as to tell those who would step, ride or just potter into your path that you are there, and that you won't be stopping or turning. Third: fight the impulse to cycle as if you were aiming to get from A to B, and affect a rambling, indirect approach. Fourth: do not ever stop, except for policemen: it only confuses people. I am too tall and impatient for this, however. The archives are a 35-minute ride away, and although I rein in the speed to half my north London norm, I cannot cycle as slowly and accidentally as the Shanghai masses. Life, well, research time, is just too short.

Sunday

I find myself on the Bund. The Huangpu river still heaves with speeding boat traffic. The waterfront 1930s high-rises, Victor Sassoon's Cathay Hotel, the Hong Kong and Shanghai Bank, the customs building - Harold Acton's "pompous toadstools" - still stand magnificently, symbolising the city for foreigner and Chinese alike. Opposite the Bund stands the hideous Orient Pearl TV Tower. Still, the view must be good, and it's a clear day. I'm looking for a cotton mill which used to be around here somewhere. Joy of joys, there it is: the Shanghai No. 10 mill still exists.

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Tuesday

My bemused fixers have arranged a visit to the No. 10, once the British-owned Lunchang Mill, established in 1933 and the site of a bitter strike in 1939. It was the final workplace of one of my policemen. Old and new Shanghai combine: the No. 10, losing money for years, closed down in October 1996. Its 1930s buildings are to be demolished in August to be replaced (unusually) with a park and riverside walk. Peng shifu (Master Peng) is 80 and has been located to talk to me about the strike and the policeman. Peng remembers him well as a lout and a drunk.

Friday

Last day - a morning dive into the archive for a wonderful file on 1920s gambling that emerged yesterday. Then sightseeing before an evening flight. And so to Hong Kong - a vital coda to the research, but one that is changing as the clock ticks on to June 30.

Robert Bickers is a research fellow in modern Chinese studies at the University of Cambridge.