If I mention the word "radical", please don't stop reading. Yes, I admit, it does normally herald a numbing passage about "constitutional reform", "welfare reform", or any other kind of "reform". "Reform" is always "radical". And very often, dare I say, it's nothing of the kind.

Forget the changing status of countless non-entities in the House of Lords. Forget the changes to the primary school curriculum. Forget the Scottish Parliament and the Welsh Assembly. Forget the Mayor of London (to be). Forget the absurdly-named "Drugs Czar". There is only one truly "radical" show in town. It's this week's big story.

Stay with me. Don't be put off. It's... social security!

Nothing to do with you? Wrong! If you're not receiving any benefits, you're probably paying for them. Benefits cost every family £80 a week. How do I know? Well, Tony Blair says so. The figures are official, and they're the most up-to-date available.

Benefits cost over £100 billion a year. That's one hundred thousand million pounds a year. Crooks who cheat the system cost at least £4 billion a year. There is more spent on disability benefits than on the entire schools system in the UK.

Until this week, caring, sharing, compassionate, hyper-efficient New Labour found itself accused of cruelty and political cack-handedness. All the grand talk about reforming the welfare system had boiled down to an attack on single parents -- and even on the disabled! Hundreds of Labour MPs were sick as parrots, and dozens rebelled against the party line.

It's so easy to get bogged down in specific policy changes, and rather more difficult to see the bigger picture. What Labour is planning to do is change the way we all THINK. No mean feat. Decades of thinking on welfare and benefits is to be turned upside down. And vast numbers of the British middle class will find the changes difficult to take.

The message is becoming clearer by the day. First, Labour wants to kill any suggestion that it's not concerned with protecting the poor. As Mr Blair said in his big speech in the Midlands on Thursday night: "All those in genuine need will always be helped and supported by this Labour government -- that is my guarantee to you as leader of the Party."

Second, the bill for that protection will go to those on "higher" incomes. Mr Blair believes that too many people on "higher" incomes are receiving benefits which might be better spent elsewhere. The big problem, to which he provided no solution in his Midlands speech, is how to define "higher" income.

My guess is that many voters who consider themselves to be on "modest" incomes, and who have "modest" savings (if any at all), will be horrified to learn that by New Labour standards they are on "higher" incomes. They will learn that Child Benefit, for example, will probably be taxed in their case.

Those "higher" earners with disabilities will learn that they might well lose some of their disability benefit. And maternity benefits will almost certainly be capped for those on "higher" incomes. The proceeds could be switched to low-paid mothers who don't (as things stand) qualify for maternity pay. The state pension would also be skewed to protect the poorest.

All this conjures up one of the most provocative concepts in welfare -- the Means Test. Many Labour MPs would rather be fed a diet of cockroaches than embrace means-testing, which is why Harriet Harman (Social Security Secretary) is already trying on a blatant play with words. She's now talking about subjecting better-off recipients to an Affluence Test. Will this wash? It might if the definition of "higher incomes" means that millions of middle-class families aren't badly hit.

So this has been an important week for Mr Blair. He can't hope to win the argument over welfare reform if the debate is forever couched in terms of "betraying socialist principles", "punishing the poor", or "attacking the sick". This is why the weeks before Christmas were so disastrous for the Prime Minister and his colleagues. It was a good lesson for those who've convinced themselves that they have nothing to learn about presentation.

Above all, Tony Blair wants an open, informed debate. His "Welfare Roadshows", the first of which was Thursday night's Midlands experience, is meant to raise that debate beyond the so-called "scaremongering" of opponents. He isn't confident his ministerial colleagues can win over the voters, so he's tackling the job himself. Some have compared it with his crusade to jettison Labour's old Clause 4, the party's former commitment to widespread nationalisation.