Birth control existed but there were drawbacks. Condoms were far less sensitive and easy to use than they are today. The cap was fiddly and hindered spontaneity. The rhythm method was unreliable, as was the withdrawal method. Nevertheless, the other options were so unattractive that more than half of British couples were using the withdrawal technique well beyond the end of World War II.
The introduction in 1961 of a reliable, convenient oral contraceptive pill available on the National Health Service was a godsend to British women. But the medical establishment wasn't quite ready to embrace free love in 1961. When the Pill was first introduced it could only be prescribed to married women. This didn't change until 1967.
The drug worked by giving the body an extra boost of hormones (synthetic oestrogen and synthetic progesterone in the first Pill), to prevent ovulation. Used correctly, the Pill was, and remains, remarkably effective - far more reliable than any other method. Fewer than one woman in 100 per year of use will become pregnant while taking an oral contraceptive.
Since the 1960s, medical researchers have identified some side-effects to the Pill. But these weren't known about in 1961. When it was introduced, doctors regarded the Pill as completely safe, adding to its appeal. It was highly successful from the outset: by 1964 half a million British women were taking the Pill and the birth rate actually began to fall.
But there were other, more subtle consequences. Free from the fear of pregnancy, young people could make love without getting married. Couples began to "shack up" together. Some individuals chose to have multiple sexual partners. Victorian attitudes to sex imploded under the assault of the swinging sixties. Women on the Pill were at the forefront of that assault.