But now the south London heath is surrounded by suburbs, heather has been replaced by mown grass and the air is heavy with traffic fumes. Here, as elsewhere, the toads have been wiped out by a combination of habitat loss and air pollution.
There are only about 20,000 breeding adults left in Britain, scattered among some 40 sites in England and Scotland - it had become extinct in Wales. But the amphibian has now been included in rescue plans for 114 animal and plant species, drawn up by a committee of government conservation scientists, wildlife groups, land-owning interests and civil servants.
The species is common in Spain, but in Britain it seems unable to compete with the slightly larger common toad and frog. It can only hold its own in sandy habitats such as lowland, cattle-grazed heaths and dunes.
During hot days the toad buries itself in sand to keep cool. It hunts at night, running rather than hopping after its insect prey amid sparse vegetation. It is the noisiest British amphibian, with the males' throat swelling up to ping-pong ball size to produce a loud croak.
Both heath and dunes have declined rapidly this century. Much of the heathland has disappeared under housing and forestry plantations or been invaded by scrub and bracken, while many dunes have become covered by dense vegetation.
Many of the shallow ponds where it spawns have also gone. Conservationists believe acid rain caused by pollution has contributed to its misfortunes.
But the natterjack can make a comeback, as a pilot species rescue programme run by the Herpetological Conservation Programme has shown. The toads were reintroduced to 13 suitable or formerly occupied sites, including one in Wales.
The committee proposes that its numbers should be maintained at their 1970 level at all sites where it is still found, and that it should be reintroduced to at least five more sites. The most important point is to make sure landowners know what sort of habitat the toad needs, and encourage them to manage their land appropriately. The cost is put at pounds 37,000 a year.