The move took Express Newspapers owner Richard Desmond by surprise as Hill, who replaced Rosie Boycott, resigned yesterday.
The official line at Express Newspapers is that Williams leaves on good terms with Desmond, but his choice of next job can not have gone down well with his boss, who is fighting a running battle with Associated.
Williams first joined the Express in 1977 where he worked for 10 years, rising to the position of features editor. He then joined the Daily Mail, where he was also features editor. He rejoined the Daily Express in 1995 as executive editor.
"I have had three years as editor of the Express but I am absolutely delighted to have the opportunity to rejoin a company, which loves jouralism and invests in it. I feel like I'm coming home," said Williams.
He leaves the Daily Express with a flat circulation. In November's ABCs, sales were up by 0.6% to 950,373, while the Daily Mail rose 0.22% to 2.48m.
With a small dig at Express Newspapers, Paul Dacre, editor-in-chief of the Daily Mail, welcomed Williams back to the Daily Mail. He said: "I'm delighted that Chris, a journalist for whom I have the greatest respect and who has done so well at the Express with such limited resources, is rejoining the group as editor of the Scottish Daily Mail."
Prior to becoming editor of the Daily Express, Williams was executive editor under Boycott, who departed two months after the newspaper group was sold by United News & Media to Northern & Shell owner Desmond.
Boycott, the former Independent editor, had been editor of the mid-market tabloid for two years and was responsible for shifting the title's political bias from right-leaning to centre left.
Under Williams, the paper's circulation slipped below the 1m mark and has failed to climb past the figure again.
Williams was also responsible for helping Northern & Shell shed hundreds of jobs, which were cut in the wake of Desmond's takeover of the paper.
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