The complicated publishing history of this influential British science-fiction magazine began in 1936, when Maurice K. Hansen began a fanzine called Novae Terrae (Latin for 'new worlds'), which ran for twenty-nine issues before Hansen, finding the project too time consuming, handed it over to editor John Carnell. Carnell re-named the publication New Worlds, and restarted the numbering system. This version of the publication ended in 1939 with the outbreak of World War II, after only four issues.
Carnell restarted the periodical in 1946, publishing it as New Worlds, with the subtitle "Fiction of the Future.' Under his editorship the magazine ran for nearly twenty years and held a monthly publication schedule from 1954. In 1963, Carnell decided to close the magazine, but the intervention of fan and writer Michael Moorcock instead saw it sold to publishers Roberts & Vinter, with Michael Moorcock established as editor from 1964.
New Worlds went into receivership in 1967, but returned after a brief hiatus, thanks to an Arts Council grant. This version lasted only four years, before folding in 1971. Revived again (again by Moorcock) in 1971 as an anthology paperback called New Worlds Quarterly, the magazine couldn't sustain the quarterly publication schedule and folded after ten issues (in 1976).
Since then, New Worlds has been revived as a semi-prozine in 1978 (which folded in 1979, after five issues) and as an annual trade paperback in 1991 (which folded after four issues plus one-off issues in 1996 and 1997).
According to Mike Ashley,
'From this fourth issue [of the post-war revival version], New Worlds started to develop its own character. It was sufficiently different from its American counterparts to be distinctive. Although its size, format and policy echoed Astounding, there remained a typically British atmosphere about it. The covers were subdued, thus making them more appealing to the general reader rather than the more juvenile elements who were attracted by the brash action covers of most 1940s American pulps. It is almost certain that the average age of readers of New Worlds, as with Astounding, was older than that of readers of the other sf pulps. The stories also had a strong British flavour.' (The Time Machines: The Story of the Science-Fiction Pulp Magazines from the Beginning to 1950, Liverpool University Press, 2000, p.205.)
[For further details see the "New Worlds" entry published inline by Galactic Central Publications]