From 7 November 2011, the programme was extended in length to 45 minutes (from 30 minutes). This has meant the thirty-minute programmes at one time broadcast immediately after The World at One (such as Brain of Britain) have now found a new time slot on the Radio 4 schedule. A fifteen-minute programme now fills the gap till 2 pm.
The programme began on 4 October 1965 on the (then) Home Service and its launch is considered to have been key in making news programmes 'appointment to listen' broadcasting. As the then head of BBC Radio, Jenny Abramsky, noted, the programme started at a time when the Today programme was still in a more comfortable magazine format. The World at One "broke new ground in news broadcasting and was one of the reasons why radio is still important today", helping establish a form of current affairs programme that influenced the creation of Newsnight in 1980 and Channel 4 News in 1982.
The launch of The World at One was part of a wider change in BBC news and current affairs coverage: more journalists were arriving from Fleet Street and replacing a more sedate and collegiate culture. John Timpson said that by 1966 or 1967, "n Oxbridge accent was no longer as important as a good contacts book, a shrewd eye for a new angle, and a skin like a rhinoceros" and that the news offices "no longer had the leisurely atmosphere of a club smoking room".
The programme had attracted criticism as it seemed to blend together news and current affairs, and break down the distinction made between reporting and interpretation. David Hendy, in Life on Air: A History of Radio Four, said that this change was more a change in aesthetic than it was in underlying organizational structure: "by allowing the programme presenter to write and deliver the headlines, it did appear to blur it on air". In his history of radio news and current affairs, "Public Issue Radio", Hugh Chignell pointed out that The World at One was a highly successful but also a profoundly controversial innovation. It provided a successful approach to news and current affairs which would be cloned elsewhere but at the same time it horrified the more Reithian wing of the BBC who reacted in the 1970s by creating single subject current affairs programmes (Analysis and File on Four) in reaction to The World at One's vulgar journalism. That vulgarity was personified by its first presenter, William Hardcastle, who was a former editor of the Daily Mail and had also been Washington Correspondent for Reuters. The Radio Academy Hall of Fame says he "had a businesslike, but warm broadcasting voice, and a style that emphasised fact rather than comment, bringing some Fleet Street urgency to the radio presentation of news". Hardcastle did not want to do the programme every day so Andrew Boyle suggested he share the job with William Davis another presenter whose career did not wholly depend on the BBC.