The case of Joanna Yeates is a very sad one. Her body was found in a snowy lane in the West of England eight days after she was reported missing from her home in Bristol.

Police changed their inquiry from investigating a missing person to looking for a murderer.

Her parents have acted with a heart-aching dignity, hoping someone would give detectives the information required to make a significant breakthrough and arrest. It is a case which has dominated the UK media throughout the quiet Christmas/New Year period.

The police service running the operation - Avon and Somerset  - have used the media extensively, appealing for information, keeping the case in the public eye.

On Wednesday, it called another news conference, but as journalists lined up to go in to the room where it was to be held, the representatives of one UK national broadcaster, ITV News, were told they would not be allowed access.

Now, I'm not there, but a number of friends are covering the story for a number of other news organisations. They were shocked at the decision.

When asked why, the police said the chief constable was apparently unhappy with the tone of a report broadcast on Tuesday evening which was critical of the organisation.

This may seem like a minor issue but it is an attack on the free press.

The police - a publicly funded body, which is ultimately answerable to a local police board made up of locally elected politicians - has decided that in order to get access to information on a prominent case, journalists must not criticise them.

It is a move which smacks of something that would be experienced in some tinpot dictatorship rather than a country where a free press is necessary and essential to hold those in power to account. It is important that this case is highlighted.

We lose our civil liberties not in huge sweeping moves but rather in almost unnoticeable increments.

The police in Bristol have hampered their inquiry by cutting out a national broadcaster with an audience in the millions.

But they have also made a sneak attack on a free media - and this should not be quickly forgotten after they hopefully find Joanna Yeates' killer.