Thank you for downloading more or less from the BBC. This is the version of the programme

first broadcast on BBC Radio 4. Here's Tim Harford.

Hello and welcome to more or less, the programme which refreshes the numbers

other programmes cannot reach. This week, this man is planning to make an unusual gift

and he wants to know how much it's worth. I think we were actually behind the pool,

we need to leave and I think I want to give away my kidney.

But first, following the killing of drummer Lee Rigby in Woolwich,

the security services have been criticised because it transpires the suspects were known to them.

Surely they could have been followed around shouldn't the security services be paying more attention

to people who are known to be dangerous. Parliament's intelligence and security committee

is to investigate the case. While I've been speaking to the former head of MI5,

Dame Stella Rimmington, is this sort of criticism I asked, reasonable?

Well, if the implication of that criticism is that the security service should know

everything that everybody who is known to them is doing every hour of every day,

then it clearly isn't reasonable. I mean, I don't know how many suspects there are, but let's say,

I want to show this in the newspaper that there are about 2000. And if you want to follow

an individual around 24 hours a day, you would probably need a team of, let's say, six people.

And that's probably underregging it with cars so that they would be ready either to follow

this person away if he went out in a car or to leap out the car and follow him if he was on foot.

But that team of people would work for, let's say, six hours a day. So you need to do it 24 hours

a day. You need three shifts of that for one person. And then you might need other people,

statics events, people sitting in a house, for example, to alert these people when the

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