Abortion only became legal in general terms, and under certain circumstances in Britain (exc N Ireland) in 1967 with David Steel's Abortion Act: the case that Jim cites may have been legal, but was probably a one-off for extenuating circumstances in that particular case - but was not a general legalisation of abortion in England, Wales and Scotland: that had to wait for 1967. In the meantime, between 1931 and 1967, many women suffered the devastating, sometimes fatal, effects of illegal abortion.
Provision of contraception and advice on the use thereof is vital, but there is no 100% cast-iron guaranteed method (other than total abstinence) and failures of contraception do occur.