O2 boss Ronan Dunne has announced he is leaving the company after 15 years with the group, eight of which were spent at the helm.
Dunne will step down from the board of O2 owner Telefonica UK, a subsidiary of Spain's Telefonica, on 31 July. He will be replaced by finance chief Mark Evans, who joined the group in January 2012.
Dunne, who is the telecom company's longest-serving chief exec, said on Twitter that it had been the "greatest privilege" to lead the firm.
"I am hugely excited by the opportunity to lead O2 through its next chapter," said Evans.
"O2 has a track record in redefining itself to keep pace with technology change and customer demand, and has an enormous amount to offer within the evolving telecoms market. I’m very much looking forward to maintaining the momentum in the business and striving to make our customers the most satisfied in the UK, long into the future.”
Telefonica chair José María Álvarez-Pallete added: "Mark’s contribution as CFO has been instrumental in delivering revenue and profit growth over the last four years and I know the business will be in good hands with him as leader.
“I would also like to take this opportunity to thank Ronan for his outstanding leadership, dedication and achievements not only as O2’s longest serving CEO but his support and contribution as a member of the group executive to Telefonica’s transformation journey. He has led the O2 brand to achieve great things on behalf of its customers, employees and shareholders and built a team of talent to be proud of. I wish him all the best for the future.”
Telefonica is reported to be considering an IPO - which could give O2 customers the option of buying shares in the firm. The flotation plans follow a failed attempt by Three to take over the network, after the European Commission blocked the proposed deal earlier this year.