Editing Viscount (section)

====Use as a courtesy title====
A specifically British custom is the use of viscount as a [[courtesy title]] for the heir of an earl or [[marquess]]. The peer's [[heir apparent]] will sometimes be referred to as a viscount, if the second most senior title held by the head of the family is a viscountcy. For example, the eldest son of the [[Earl Howe]] is [[Viscount Curzon]], because this is the second most senior title held by the Earl.<ref name="Debrett's: Courtesy Titles">{{cite web|title=Courtesy Titles|url=http://www.debretts.com/forms-address/titles/courtesy-titles|date=n.d.|publisher=[[Debrett's]]|access-date=18 June 2014}}</ref>

However, the son of a marquess or an earl can be referred to as a viscount when the title of viscount is not the second most senior if those above it share their name with the [[substantive title]]. For example, the second most senior title of the [[Marquess of Salisbury]] is the [[Earl of Salisbury]], so his heir uses the lower title of [[Viscount Cranborne]].

Sometimes, the son of a peer is referred to as a viscount even when he could use a more senior courtesy title which differs in name from the substantive title. Family tradition plays a role in this. For example, the eldest son of the [[Marquess of Londonderry]] is Viscount Castlereagh, even though the Marquess is also the Earl Vane.

On occasion, the title of viscount may be the courtesy title used for the grandson of a duke, provided that he is the eldest son of the duke's eldest son.  This is because the eldest son of the duke will be given the second-highest title of his father (marquess or earl), and so the third-highest is left for his eldest son. It is possible for the great-grandson of a duke to hold the courtesy title of viscount if the duke's eldest son has the courtesy title marquess and his eldest son, in turn, uses the title of earl.