Misc: What letter represents the number 500 in Roman Numerals?

Questions

Captain John Mason received a grant for land in 1629. He named this land after the English county of Hampshire where he had enjoyed a number of years as a child?

What is the full name for Economy Class Syndrone (DVT)?

MMR the vaccination, what does it stand for?

Wet wet wet had a no 1 hit in the 90s with Love is all Around, how long did it spend at the top?

Name of Wet wet wets front man?