This afternoon, the Information Commissioner will unveil a code of practice for data anonymisation. His office is under pressure; as I described back in August, Big Pharma wants all our medical records and has persuaded the Prime Minister it should have access so long as our names and addresses are removed. The theory is that a scientist doing research into cardiology (for example) could have access to the anonymised records of all heart patients.

The ICO’s blog suggests that he will consider data to be anonymous and thus no longer private if they cannot be reidentified by reference to any other data already in the public domain. But this is trickier than you might think. For example, Tim Gowers just revealed on his excellent blog that he had an ablation procedure for atrial fibrillation a couple of weeks ago. So if our researcher can search for all males aged 45-54 who had such a procedure on November 6th 2012 he can pull Tim’s record, including everything that Tim intended to keep private. Even with a central cardiology register, it’s hard to think of a practical mechanism could block Tim’s record as soon as he made that blog post. But now researchers are starting to carry round millions of people’s records on their laptops, protecting privacy is getting really hard.

In his role as data protection regulator, the Commissioner has been eager to disregard the risk of re-identification from private information. Yet Maurice Frankel of the Campaign for Freedom of Information has pointed out to me that he regularly applies a very different rule in Freedom of Information cases, including one involving the University of Cambridge. There, he refused a freedom of information request about university dismissals on the grounds that “friends, former colleagues, or acquaintances of a dismissed person may, through their contact with that person, know something of the circumstances of that person’s departure” (see para 30).

So I will be curious to see this afternoon whether the Commissioner places greater value on the consistency of his legal rulings, or their convenience to the powerful.