Harrison, the managing director of TalkTalk Consumer, has been at TalkTalk for seven years and will succeed Harding in May. She was a key player in the launch of TalkTalk in 2003 and was its group marketing director between 2003 and 2008. She became commercial director
She was a key player in the launch of TalkTalk in 2003 and was its group marketing director between 2003 and 2009, before becoming commercial director. Harrison (née Clark) was appointed managing director of TalkTalk's consumer division in 2014.
TalkTalk also announced that its founder Sir Charles Dunstone will become the company’s executive chairman in May after stepping down as chairman of Dixons Carphone later this year. He will remain as a senior advisor to Dixons Carphone and be replaced as chairman by Lord Livingston, the former BT chief executive.
The company announced the changes alongside its third quarter trading update, which showed group revenue dropped 5.2% to £435m year on year.
TalkTalk blamed "short-term" impacts on the quarterly revenue, such as a repricing of contracts and a high level of contract renewals that came with cheaper deals.
Meanwhile Charles Bligh, the managing director of TalkTalk Business, will become chief operating officer.
Harding took charge of TalkTalk in October 2010 and was chief executive in 2015 when hackers stole confidential customer data, prompting the company to suspend its advertising. TalkTalk estimated the cyber-attack cost it up to £35m.
Dunstone said: "Dido has been a tireless, energetic and effective force for good from the day she joined TalkTalk. As a result of her leadership and total commitment to all of us who work here and our customers, she has helped transform TalkTalk into a much stronger business. She leaves with our thanks and very best wishes for the future.
"I'm excited at the prospect of spending more time on TalkTalk, beginning with delivering another successful performance this year; and I am delighted to announce the promotion of Tristia and Charles to help me lead the business so that we continue to deliver successfully for our customers and our shareholders."