What's the point of a diary if you can't read it?

Can't they look in the diary and go "that's in South London, that's in South London, that's in South London" and then just add them up?

Simon Hughes: To ask the Prime Minister what visits he has made to hospitals in South London since the last general election.

The Prime Minister: Records of official visits are not held in the format requested. My visits cover a range of matters including health, education, criminal justice and the economy and I have visited a number of hospitals since 1997.

Surely can't take that long to look in a diary and count can it? I mean, they haven't said it will cost too much to get the answer in the "format requested" have they? Unless of course there is an internal document destruction policy at the moment?