Adly Mahmud Mansour, the head of Egypt's Supreme Constitutional Court, has become the country's interim leader following the removal by the military of Islamist President Mohammed Morsi.
The armed forces suspended the constitution on 3 July and the commander-in-chief of the armed forces, Gen Abd-al-Fattah al-Sisi, announced that Mr Mansour take on presidential duties until fresh elections are called.
Having served as deputy head of the constitutional court since 1992, Mr Mansour was appointed as its president in May 2013 and took up his post on 1 July.
As he took the oath as interim leader, he praised the massive street demonstrations that had led to Mr Morsi's removal.
"The most glorious thing about 30 June is that it brought together everyone without discrimination or division,'' he said.
The revolution, he said, must go on so that "we stop producing tyrants".
Egypt's Masrawi website describes Mr Mansour as a "mysterious" man with a low media profile.
Born in Cairo in 1945, he received a licence to practise law from the Cairo University in 1967 and joined the state council in 1970, rising in the ranks until he was appointed deputy president of the constitutional court in 1992.
He headed the constitutional hearings in 2012 that scrapped the "political isolation" law, which prohibited members of the old regime from contesting elections.
It is this law that allowed Mubarak-era prime minister Ahmad Shafiq to run as a candidate in the last presidential elections.
Mr Mansour's name seems to have first emerged as a possible leader of Egypt on 30 June.
On the first day of the current wave of protests on 30 June, a group named "Al-Sha'ab Yureed" (The People Demand) distributed a petition among fellow protesters calling for the formation of a presidential council to run the country, listing his name as a possible member.
The Masrawi website notes that this is a time of "rapid change" for Mr Mansour, a man who has spent the last 10 years "playing the role of second-in-command" in the court.
Before his appointment, Twitter users embraced the possibility of Mr Mansour becoming interim president.
Speaking to Al-Ahram Al-Shabab, Judge Hamid al-Jamal described Mr Mansour as "a quiet, calm man who makes balanced decisions and who will respect the will of the Egyptian people".