Lady Mayoress - of a City
ENVELOPE: "The Lady Mayoress"
OPEN: "Madam" or socially "Dear Lady"
CLOSE: "Yours faithfully"

Lawyers - Queen's Counsel
ENVELOPE: "[Edward Smith] Esq, QC.". Do not add "QC" if a High Court Judge.
OPEN: "Sir"
CLOSE: "Yours faithfully"

Lord Advocate
ENVELOPE: "The Rt Hon the Lord Advocate"
OPEN: "Sir"
CLOSE: "Yours faithfully"

Lord Chancellor
ENVELOPE: "The Lord Hon the Lord High Chancellor"
OPEN: "My Lord"
CLOSE: "Yours faithfully"

Lord Chief Justice
ENVELOPE: "The Lord Chief Justice of England,"
OPEN: "My Lord" or "Your Lordship" when addressed in Court, otherwise "Sir". Unless also a peer, then use the relevant opening.
CLOSE: "Yours faithfully"

Lord Mayor
ENVELOPE: "The Right Hon the Lord Mayor of ...." for London, York, Belfast and Cardiff. Other Lord Mayors in the UK "The Right Worshipful the Lord Mayor of ....."
OPEN: "My Lord," or "Dear Lord Mayor,"
CLOSE: "Yours faithfully"

Lord Mayor's Wife
ENVELOPE: "The Lady Mayoress"
OPEN: "Madam" or socially "Dear Lady,"
CLOSE: "Yours faithfully"