If you're not already an admirer of London's underground network and its finery, I may have difficulty in persuading you of the wonders of the Waterloo & City line. Known to its thousands of daily users as 'the drain', it's hardly the most obvious charmer on paper:

But for me, what links the eastern end of Waterloo station with the heart of our City is actually the eighth wonder of the world - and always will be, it seems.

Its appeal is partly one of anomaly. A freak of rail nationalisation in the 1940s saw the Waterloo & City become the only underground line to be operated by British Rail (rather than London Transport, as was then), so the feel has always been so different to any other tube line. It's also completely isolated from the rest, and the trains have to be hoisted above ground for non-routine maintenance by a crane. More on that coming up.

As a boy, the W&C was always top of my wish list for a visit whenever I was taken to London (wasn't it yours?), and I came to know the whole thing inside out: the quaint little purpose-built '40s trains, with their wooden panels and the warm glow of tungsten bulbs; every twist and turn of the two tunnels, which seemed to take you endlessly left then right as you made your way under the Thames; and even the most minute details of the two stations - the odd tiling on the wall of Bank station, and the little embossing of the Network SouthEast logo on the platform edges at Waterloo.

For an 8-year old, it was a journey made entirely for pleasure. I have photographs at home of a little David beaming from ear to ear, having been allowed to ride inside the driver's cab of one of the trains (number 58, if you really care). I remember it well.

The W&C charm even remained through the rail privatisation era (few lines can boast that, though many have since had a charm renaissance), when London Underground inevitably took over. Admittedly, a little of the magic had been lost with the scrapping of the older trains a year earlier, replacing them with new Central Line lookalikes that didn't quite win my favour initially. But they were still very different up close, and with little investment forthcoming for the line as a whole, things remained pretty much as they always had done.

So imagine my horror when, earlier this year, it was announced that the line was to close. Okay, so only for a few months while major rebuilding and modernisation work was carried out, but this would probably be the end of the line as I knew it. In case it should come back unrecognisable, I went along on the final day of the 'old' line, just to say my goodbyes.

Yesterday, I had my first opportunity to sample the newly reopened line, and how surprised I was. Tiles at Bank, platform edging at Waterloo, that wonderful, unique charm, all... still there!

There certainly is much evidence of modernisation; the trains have been newly painted (albeit in standard LU livery), the ride around those bends is now much less bumpy than I remembered, and finally the London Underground branding has made it to both trains and stations. But otherwise, Dr Progress has left well alone. The fabric of the line has been mercifully upgraded to ensure its future, but the character remains distinct. And long may it so do.

If you haven't yet ridden the Waterloo & City line, then do it - you might see what I mean.

But if all else fails, be sure to look at Metronet's fantastic videos of the trains being hoisted out of the line's own depot for refurbishment, and then dropped back in again with the job done.

London SE1 also has some good photos.

I think even the most cynical of London Underground users will be impressed.