Finally, it's going to be cool to ride the London Underground

London

The next Tube to arrive on platform two will be really chilled and comfortable. Passengers are therefore advised to wrap up warm, with bobble hats, sweaters and tights for the 17-minute trip to King's Cross.'

OK, as far as London Underground platform announcements go, this message to travellers seems pretty unlikely. Even on mildly sunny days, the rush hour Tube is a maelstrom of clammy commuters, all packed in like sardines in trains, replete with a ventilation system involving a small grate the size of a matchbox positioned, rather ironically, just above the hoarding flogging ice-lollies and cool drinks. In future, however, it might not be so hot. At least not for some.

As London experienced a prolonged mini-heatwave - what the Met Office likes to call an 'Indian summer' but which is redolent neither of India nor of summer - Mayor Boris Johnson unveiled the new, long-awaited 21st-century Tube train boasting ... wait for it, wait for it ... air conditioning.

That's not all. The trains, which will cost GBP8.5 million (HK$115 million) each, herald what Tube chiefs hail as a revolutionary design: the carriages have no internal doors linking each carriage. In future, it's just one continuous 'tube', allowing the cooler air to whoosh down the train and chill everyone out all at once. (Think MTR trains but with chintzy seat covers, not polished steel.) What's more, the extra space allows 20 per cent more space for a fifth as many passengers.

The mayor said because LA and NYC had them, then Londoners had to have them, too.

Well, not everyone in London.

From 2010, only travellers on the District & Circle lines, the Metropolitan line and the Hammersmith and City line will benefit - the shallow, cut-and-cover Tube lines dug in the mid-19th century to accommodate steam trains, traditionally slow lines which cater for just 40 per cent of the network. It will also take five years to roll out all the cool new trains.

And for those on the other lines? Well, they will have to soldier on.

Underground lines, including the Victoria, Piccadilly, Northern, Jubilee and Bakerloo, are too snug to carry the roof-mounted units and too deep for vents to dispense all the hot air that air con units dispel.

Still, Tube chiefs are leaving no stone unturned to help cool passengers, with engineers planning to tap into London's subterranean waters, such as the Tyburn river, to help cool stations naturally.

It's not just the Tube feeling the heat recently, with the new TX4 black cab having developed a slight problem: it blows up.

Well, not 'blows up', per se. Seven cabs have spontaneously caught fire over the past few weeks, either idling in jams or awaiting fares, with a further four catching fire across the UK, prompting Coventry-based London Taxis International to recall 600 suspect cabs from a 2006 batch. Transport for London, the capital's governing transport body, has also suspended their owners' licences until their cabs are checked out.

No one seems to know the cause, only the effects - a fire without warning giving the driver just 45 seconds to abandon cab.

It may seem funny, but passengers and cabbies are not laughing. The internal locks on cab doors automatically seal shut as the fires trip the electrics, potentially trapping passengers. It's enough to make anyone commute by bicycle.

Tomorrow: Sydney