There are more than 100,000 public bodies in Britain that are subject to the Act.

They include NHS bodies and GPs, universities, museums, regulators, the BBC and Channel 4 (except where information relates to their journalism), devolved assemblies and private bodies.

Requests can be made in writing, by e-mail or by fax.

When making an application, individuals must describe the information required and specify how they want to receive it but there is no need to give a reason for the request. Nor is there any need to mention the Freedom of Information Act, though it is advisable to do so.

All officials on public bodies should have been given FoI training and should know that they have a duty to assist.

The public is able to ask for any recorded information, in whatever form it takes, from e-mails through to tape recordings.

The Act is retrospective, meaning that as long as it exists, you have a right to see information whether it is a month or 50 years old. You also have the right to get information from databases.

There is no charge to make a freedom-of-information request beyond photocopying and postage, but any application that would cost more than £600 to comply with can be refused or a payment demanded.

The success of the Act will be judged by many on how widely the exemptions are enforced.

Some categories of information are “absolutely exempt” under the Act, which means that the public authority need not confirm or deny the existence of, let alone disclose, the information.

Absolute exemptions apply to several bodies involved with national security. These include security and intelligence agencies, the National Criminal Intelligence Service, special forces, courts and tribunals and Scottish authorities.

There is also an absolute exemption on information held by the Houses of Parliament which, if disclosed, could prejudice Cabinet collective responsibility or inhibit free and frank advice or discussion about public affairs.

It also bans the disclosure of personal data of which the applicant is either either the data subject or where it might contravene the Data Protection Act, or material which would constitute an actionable breach of confidence.

There is a further category of “qualified exemption”, where the public authority can withhold the information but only where to do so would be in the public interest and would outweigh any public interest in disclosure. The 20-day working time limit does not apply.

Qualified exemptions include information intended for future publication; that needed for safeguarding national security and which would prejudice national defence; and that held for criminal investigations.

There are also several provisions that protect the inner workings of the Government. These include a qualified exemption for material which relates to the formulation of policy, ministerial communications, law officers’ advice or communication with the monarch.