an inspector from Scotland Yard

Scotland Yard was created in 1829.

Murder at Scotland Yard was created in 1953.

Scotland Yard, the headquarters of the London police, is so called because it used to be in a street called Scotland Yard.

Not sure what you mean. Scotland Yard is the name of a street in London. The Headquarters of the Metropolitan Police are known as New Scotland Yard (although they're not located there) but the majority of people just call it Scotland Yard.