The trust black cab-drivers have built up will be dented if a convicted killer gets his licence
There's a scene in Taxi Driver, Martin Scorsese's classic 1976 film, in which Robert De Niro, a taxi-driving Vietnam vet, shoots his way into a bordello. He then lays waste to pimps, bouncers and clients as he avenges the girl prostitute he's become obsessed with. Incredibly, her parents, and the media, hail him as a hero. The final shot is of De Niro, back at work, looking mad and dangerous at the wheel of his taxi.
Or should that be a London cab? Transport for London, the body that regulates the cab trade, wants to let a paranoid schizophrenic killer take the cab drivers' test, the Knowledge.
The unnamed man was jailed indefinitely for manslaughter in 2001 after strangling his wife. He was released after the parole board determined that he was no longer a risk to society.
The proposal would give new meaning to the term "Not Safe in Taxis", currently used to describe a lecherous date. Cabbies plan to protest. "This will affect the trust we have built up over hundreds of years serving the London public," says Grant Davis, of the London Cab Drivers Club. His concern is admirable and, ultimately, well-placed.
The trouble is that Davis has a rather sentimental take on the cabbie's reputation among the taxi-using middle classes. Riding in the back of a cab gives rise to a host of emotions beside trust. Irritation, for one: while you try desperately to use the precious journey time to read the papers for your next meeting, the cabbie feels obliged to give you a running commentary on the state of the nation.
Frustration, too, as the cab driver opts for a circuitous route, then pretends to be deaf when you remonstrate. On top of that is anxiety: the inexorable running of the meter, which means the journey from Victoria to Paddington (£15) could buy you a coat at Primark.
Also, and far too often, hailing a black cab means stepping into a world you thought long gone. Cabbies – overwhelmingly white, male and native-born – are a singularly homogenous group in our mixed society. They vent political opinions that leave good liberals hyper-ventilating, and regard the PC code as wimpy: women should be banned from driving; Muslims should go back where they belong; black people should try an honest day's work.
Yet even in the odd bubble of the black cab, changes have taken place. Cab drivers complain that they have to operate in a circumscribed environment. One told me how a drunken woman passenger passed out in the back of his cab as he was driving her home. Terrified of possible accusations and repercussions, he dumped her at the nearest police station.
Many steer clear of dodgy neighbourhoods, refuse to pick up more than one man after dark and won't do the night shift. Their reputation was somewhat dented last spring when John Worboys, a 51-year-old cabbie, was convicted of multiple charges of sexual assault.
The credit crunch has also bitten. Companies' cab accounts have shrunk; individuals think twice about hailing a cab. Minicabs, once vehicles of ill repute, have benefited from the new thrift. They charge lower fares and rely mutely and trustingly on sat navs, no matter how absurd the suggested route.
Despite their notorious griping, cabbies make a good living (to test that, ask where they spend their holidays). They have bullied their way to an exemption from the congestion charge. They can use road space that is supposedly dedicated to public transport. And the newly introduced Mercedes minibus, specially designed for them, costs less to run, is easier to drive and earns more money thanks to its six-seater carrying capacity.
But Davis is correct: they still do enjoy our trust. Cab drivers are the unofficial patrols of London's mean streets, the guardian angels who whisk your daughter to safety when she's stranded after a date turns sour at 1am. For many parents, the Saturday night ritual consists of extracting promises from the teenagers of being back by midnight and checking they've got money for a black cab.
Everyone has a "good cabbie" story. There's the Florence Nightingale who helped deliver the baby in the back of his cab; the Good Samaritan who scared off a mugger and drove the OAP victim to A&E, sitting patiently with her until she could be seen. These tales make us feel that the cheeky chappie with a heart of gold is not an urban myth and that his cab is a safe haven.
So it is all the more disconcerting, when this is not the case. Take New York. Most of the clapped-out sedans that serve as taxis in New York are like jails on wheels, with bulletproof glass and a grille separating customer from driver. In this us-against-them vehicle; the tough-talking speed-freak at the wheel seems more of a foe than a facilitator. This was even truer in Mexico City in the late 1990s. The stricken economy meant that anyone who could afford to hire one of the VW Beetle taxis risked having a knife held to their throat, followed by a demand to hand over their wallets and valuables.
Dangerous foreign taxis made us feel still smugger about our safe ones. No more. TfL may be helping rehabilitate one troubled soul by letting him learn the knowledge. But it is denting the confidence of millions who trust the black cab as a tiresome, expensive, but still indispensable institution. It seems a high price to pay.