GENERAL KNOWLEDGE: What did Robert Watson-watt invent in the 1930s?

Questions

- tables, points and bearing off used?

Who was the author of 'The Inheritors', and 'Rites of Passage'?

Which country's entire population was condemned to death by the Spanish Inquisition?

What is the length in metres of the sides of a square, which is one hectare in area?

By what name, historically, was the burning to death of people condemned as heretics by the Spanish Inquisition known?