The force has previously confirmed that an investigation is ongoing into media reporting of the Joanna Yeates investigation, or officers' conduct and interaction with journalists.
 
I would like to know:
1) Whether the investigation is still ongoing

2) When it started, and when it is likely to finish

3) What triggered the investigation, and what its parameters are.

4) Who or what body is carrying out the investigation

1) The case is still ongoing.

2) The investigation commenced in January 2011 and will continue until there is no realistic prospect of any further information coming to light.

3) Press reporting triggered an investigation as it purported to reveal information about the investigation that was not in the public domain. Its parameters are to investigate the veracity and source of such information and to deal with any criminal or police discipline offences disclosed. Also to highlight any organisational learning that would ensure operational security of future major investigations.

4) Avon and Somerset Constabulary Professional Standards Department.