On current form, the Tory party, which nobody thought had any stars bar its leader, appears to be pretty good at coming up with interesting new players. Just as David Davis, the former SAS reservist brought up by a single mother on a housing estate, exits (temporarily) stage left, in bounds his replacement Dominic Grieve, a character who in some ways is no less startling.

It turns out that the new shadow home secretary is not merely a 52-year-old French-speaking QC, but a wordsmith who has used three-word alliterative phrases 715 times in debates in the House. (This is far higher than average, apparently, and must surely indicate that Grieve has a fearsome intellect.)

Readers of last week’s Sunday Times will also know that he has a habit of solving burglaries by himself, defending vulnerable bus stops while in black tie and chucking yobs off trains.

Indeed he seems quite the modern man of action — although he looks uncannily like the lanky writer Julian Barnes. Unlike Jacqui Smith, his Labour counterpart, who doesn’t enjoy walking about the capital after dark, he is so keen to negotiate the mean streets that he frequently runs around them in the evenings. He has campaigned in illicit Brixton drinking dens, he tells me, and in housing estates where he was “occasionally threatened”. He doesn’t seem remotely perturbed about any of this.

I ask him first about his compulsion to be a have-a-go hero. Doesn’t he have faith in our police? “I have faith in their dedication,” he says, which seems a pretty wishy-washy answer.

Maybe they don’t deserve any better: after all, they didn’t exactly knock themselves out to nail the burglar who broke into Grieve’s west London home. Instead it was the MP who discovered spots of blood by the broken bathroom window, traced them up the street and thus stumbled into the robber’s den. The Met, by contrast, sent a car round and, er, that was that.

“The police were not useless,” he protests. “I can’t blame them for

not picking up bloodstains in the dark. The following morning, once I had persuaded them that I had probably, well actually, hit the bonanza point, they came back and acted promptly.”

In any case, he tells me, it’s worth remembering that “the police are citizens in uniform”. And thus, with perfect barrister’s logic, he would like me to know that the reverse can also be true. If they are us in uniform, then we can be them out of uniform. What a great way of dealing with the increase in crime on the streets.

“We have powers of arrest,” Grieve says. “We can arrest people, as citizens. If you think someone is committing a crime, you can

detain them until the police get on the scene.”

So can we all be have-a-go heroes? That sounds dangerously anarchic, as well as likely to lead to a knife in the ribs.

“We need to encourage people to be proactive,” the shadow home secretary says, skating around the question. “We are in a society where people are reluctant to be proactive because they think they will be misunderstood or not supported by the police.”

He cites the recent case of a man in Crawley, West Sussex, who detained a child for behaving badly and was then arrested for kidnap. “As long as we get examples like this, we are sending out a terrible message to the public about the extent to which they are supported. \ I’m not advocating vigilantism.” What is he advocating, then?

“People being proactive in dealing with crime. And some of \ can be resolved by giving citizens some education and training.”

Training? If the Tories get in, can we expect to be put on evening courses that will teach us how best to tackle delinquents, gangs of feral youths or drunks at bus stops? Night classes in headlocks, that sort of thing?

“Well, there is not scope for a policeman behind every lamp-post,” Grieve says. “And a lot of low-level criminal behaviour could be stopped if adults were proactive.”

Does he think we should all start going to the gym, then, to limber up for our new role as low-key policemen? After all, chucking someone off the Tube might seem like child’s play for him, but it might not be for the 23% of British adults who are clinically obese.

“People have to be responsible for themselves,” Grieve says hurriedly. “And I didn’t actually throw off the Tube. His behaviour was outrageous: he was slapping passengers on the head. He was causing a nuisance so I told him to get off the Tube, and he got off the Tube. It didn’t criminalise him but it stopped the behaviour.”

It takes quite a lot of confidence, though, to stand up and order someone off a Tube train. Having been educated at Westminster and Oxford, and then spent his entire working life in either a courtroom or the House of Commons, Grieve is undoubtedly one of those people who expects others to listen when he barks — and they probably do. However, most people are not top barristers, and making a scene in public is probably still the nation’s number-one dread.

Grieve nods. “We have to change people’s behaviour. Sometimes we are sending out signals to people not to get involved, but lots of people have confidence. My experience is that it has to do with motivation, not education. There are a lot of people out there, law-abiding citizens, who have not had a privileged education, or a privileged background at all.” Indeed.

Are we really Charlie’s Angels in waiting or, at the very least, members of the cast of The Bill in mufti? It seems we might be. In support of his idea, Grieve quotes from the report Engaging Communities in Fighting Crime, published by Louise Casey, Labour’s former “co-ordinator for respect”, this month.

“Seventy-five per cent of respondents said they wanted to do more to help the police and fight crime personally. That suggests to me that the population is not full of shy and retiring people who couldn’t care less. They do care and, on top of that, they are motivated. Not by the desire to be Rambos, but by the desire to be sensible and proactive.”

He also echoes Casey’s recommendation for “crime-mapping” — or linking statistics on specific crimes to where they occur, and making them public. “There are some things that you would not crime-map,” Grieve says. “Domestic violence in individual houses, for example. But crime-mapping for individual street areas is perfectly feasible. It would allow you to identify more locally where the problems are, and then get the police working with local communities.”

Would it go down well with the public? Imagine, say, trying to sell your house if potential buyers can see that 10 people have been mugged in your street in the past three months.

“If I may say so,” Grieve says, a trifle haughtily, “I have never come across an individual who has told me that crime-mapping will be a problem for their property values.”

As he sees it, such maps would facilitate easy identification of crime trends. “They would enable people to put two and two together. Quite a lot of crime goes unreported. I’m not going to bother reporting that my car window has been smashed in, for example. But if someone goes to the map and finds it is not an isolated incident, then the information might enable the police to solve a major offence.”

Putting two and two together, changing people’s behaviour, getting everyone to be proactive: Grieve seems rather anxious to get people as buzzily engaged in social affairs as he is. Maybe it’s because his own world has suddenly become a lot more exciting. Or maybe it’s because he senses, with slightly sweaty palms, that his political luck is in.

Get ready for local courses in how to handcuff a hooligan.

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