Public Bodies (Admission to Meetings) Act 1960

All meetings of a body exercising public functions to which this Act applies will be open to the public except where the body resolves to go into closed session. The body can only resolve to go into closed session when

"publicity would be prejudicial to the public interest by reason of the confidential nature of the business to be transacted or for other special reasons stated in the resolution and arising from the nature of that business or of the proceedings;"
Public Bodies (Admission to Meetings) Act 1960 - Statute Law Database.

A body may under subsection treat the need to consider recommendations or advice from external sources as a special reason why publicity would be prejudicial to the public interest.

"while the meeting is open to the public, the body shall not have power to exclude members of the public from the meeting and duly accredited representatives of newspapers attending for the purpose of reporting the proceedings for those newspapers shall, so far as practicable, be afforded reasonable facilities for taking their report"
Public Bodies (Admission to Meetings) Act 1960 - Statute Law Database.