Who is Black Rod and what do they do in Parliament?
As the world tuned in to watch the final sitting day of Parliament for five weeks, one individual caught the eye for social media users.
Viewers - particularly those from outside the UK - seemed bemused by the role of Black Rod, a woman dressed in black, with a gold chain and ceremonial black and gold staff.
What is the role of Black Rod?
Black Rod is best known for the State Opening of Parliament, knocking on the door of the House of Commons to summon MPs for the Queen's Speech.
When Black Rod summons MPs to the House of Lords to hear the Queen's Speech, she (or he) has the door to the Commons slammed in her face, and has to knock three times to gain entry.
Black Rod is the Monarch's representative in the Lords and the routine is symbolic of the Commons' independence from the Crown.
As well as organising ceremonial events, Black Rod, who can earn up to £93,000 a year, manages a team of 30 staff involved in the day-to-day running of the House of Lords.
Why is Black Rod in the news?
#BlackRod began trending on some social media sites this week following her role in the prorogation of Parliament.
The prorogation ceremony began when Lady Usher of the Black Rod arrived in the Commons late on Monday to lead Speaker of the House John Bercow to the Lords.
But the ritual was interrupted by some MPs shouting "no" when she asked them to make the trip.
A group of opposition MPs then made their way to the Speaker's chair to protest against the prorogation.
What are the origins of Black Rod?
The earliest known reference to the role of Black Rod as the Usher to the Order of the Garter is in letters patent - a written order from a monarch granting an office, right or title to an individual - from 1361.
There are thought to have been 60 holders of the position since then.
The title "Black Rod" comes from the staff carried by the holder - it is made of ebony and is topped with a golden lion.
The position of Black Rod also exists in Commonwealth countries Canada, Australia and New Zealand.
Who is the current Black Rod?
Sarah Clarke was appointed Lady Usher of the Black Rod in November 2017, formally taking up the role in February 2018.
She replaced Lt Gen David Leakey and, in doing so, became the first female holder of the position in its 650-year history.
Ms Clarke was previously in charge of organising the Wimbledon tennis championships.
Prior to that, Ms Clarke worked for the London Marathon, UK sport, and on four Olympic Games - including London 2012.
Accepting the role of Black Rod in 2017, she said: "I am both deeply honoured and delighted to be invited to take up the role of Black Rod."
She said the House of Lords was "a place where the smallest detail is as important as the big picture and the depth of heritage and tradition is second to none".