Guardian News & Media editor-in-chief Katharine Viner has revealed the appointment of a new number one, with the promotion of deputy editor Paul Webster as editor of The Observer.

After 20 years in the deputy’s chair, Webster is replacing John Mulholland in the role as the latter prepares to set sail for America to take up his own new role as editor of the Guardian US in April.

Viner commented: “He [Webster] has great experience, judgment and understanding of The Observer’s place in British public life and will be a superb editor for the world’s oldest Sunday newspaper.”

Webster added: “I am delighted and honoured to be appointed editor of The Observer, especially at such an exciting time in the paper’s development as it relaunches in its new tabloid format. I am absolutely committed to the progressive and liberal principles that The Observer represents, and to the high standards of journalism that my predecessors have achieved.

“I look forward to working with my colleagues to develop the new Observer as it faces up to the huge challenges of the era.”

Prior to being made deputy editor of the weekly Webster served as both foreign editor and home editor at The Guardian.

Viner was named Guardian editor-in-chief back in 2015, the first woman to be awarded the role in the titles history. This week, The Guardian also revealed its new tabloid format and accompanying advertising campaign.