The South Antrim by-election of 16 April 1970 resulted in the loss of a seat from the Ulster Unionist Party to the much smaller Protestant Unionist Party.
In the 1969 General Election the previous MP, the comparatively liberal Richard Ferguson, handily beat his only opponent, the Protestant Unionist William Beattie. Although the Ulster Unionist candidate was relatively hardline, losing his previous seat to the pro O'Neill unofficial Unionists.
Beattie first came to public attention in 1966 after he took over Paisley's Ulster Hall rallies while he was imprisoned for unlawful assembly.[1]