Having taken up the role of media relations manager this week, Holdaway is overseeing a team of four, reporting to head of comms Sue Appleby.
She replaces Natalie Yost, who joined Medway Council in Kent as media and internal comms manager in December.
Holdaway, who was unavailable for comment as PRWeek went to press, has also previously worked in a media relations manager role at premature baby charity Bliss.
Appleby joined Southwark in September 2004 after ten years at BT (PRWeek, 17 Sep 2004).
She replaced Amanda Hirst, who was Southwark’s first head of comms.