 It was during this time that the slogan "It's Scotland's Oil" came to the fore with the February election seeing 7 SNP candidates returned, rising to 11 in October.Some well known MPs such as Tam Dalyell believe this was in no small part due to the "It's Scotland's oil" slogan employed by the Scottish National Party.The economic background to the claim was the discovery of oil in the North Sea in the 1960s, and its coming on line in the 1970s.