Fareed Abdelkhalek is a living example of the Muslim Brotherhood's tenacity and appeal.
At 95, he is still a loyal member and - remarkably for a man of his age - has just finished a PhD thesis on "hisba", accountability in the Islamic system of government.
Mr Abdelkhalek first met the founder of the Muslim Brotherhood, Hassan al-Banna, in the 1940s.
It was a meeting that changed his life, Mr Abdelkhalek says at his home in Cairo.
Unlike other preachers, Mr al-Banna had a novel message - Islam was not only about praying and fasting; it was an entire way of life.
Al-Banna founded the Muslim Brotherhood in 1928 with a small group of people who wanted to rid Egypt of British control and cleanse it of all Western influence, arguing that colonialism had robbed their nation of its Muslim identity.
Branches across the country grew rapidly, with each running a mosque, a school and a sporting club. In under 10 years, al-Banna's followers grew to one million.
More than 80 years later, the founding notion of the Brotherhood - that Islam is not only a religion, but also a way of life - has become the underpinning principle of political Islam worldwide, posing a serious challenge not only to Muslim-majority countries, but also to the West.
One of the stated aims of the Brotherhood is to establish Islamic rule in Egypt. Critics also accuse the movement of spawning violent groups in other parts of the Middle East.
Despite being declared illegal in Egypt for the best part of its history, and suffering the full might of the coercive machinery of the state - emergency laws, military tribunals - it has not just survived but flourished.
'Exist to exist'
By all accounts, discipline and internal cohesion has played no small part.
"Every member of the Muslim Brotherhood is like a partner in a big company, so he sacrifices willingly," says spokesman Essam el-Erian, who has been jailed more than once.
If the breadwinner of the family is thrown in jail, the Brotherhood steps in, he adds.
"If you are facing a police regime, you are not alone. If you are arrested or if you are tortured, you find someone defending you," says Mr el-Erian.
Paradoxically, it's the threat of extinction which has been one of the main reasons for the group's ability to carry on.
But this has come at a price, says Ibrahim al-Houdaybi, grandson of one of the founding fathers and an emerging star of political Islam.
"The focus has become that we exist to exist. This led to the actual existence and growth of the Brotherhood, because any issue that we disagree on is postponed because we need to focus on our very existence at the moment.
"So it has benefited the Brotherhood organisationally but harmed the Brotherhood in terms of its ideas and objectives."
Few doubt that the failure of the state to provide for the poor has played into the hands of the Muslim Brotherhood, which now runs hospitals and charities.
But there is another kind of failure which has helped it too. In a country where normal politics has broken down after nearly 60 years of quasi-military rule, the Muslim Brotherhood retains the moral high ground.
"Now they represent the most important movement because all the political actors in Egypt have become very weak," says Amr al-Shoubaki, an expert on political Islam with the Al-Ahram Centre for Strategic Studies.
"They represent the alternative - Islam is the solution, vague and unrealistic, but for many it represents a dream for justice."
Perhaps the most obvious, and least talked about, reason for the Brotherhood's popularity and endurance is that it taps into something fundamental for all Egyptians - religion.
"The Muslim Brotherhood... anchored its identity around Islam at a time of religious renewal in much of the region," says Issandr al-Amrani, a Cairo-based Middle East analyst.
But unlike many of its critics, Mr Amrani says the Muslim Brotherhood is not an Egyptian Taliban.
"It's geared towards an idea of historical progress - the idea that Muslim countries must catch up with the West, but do so without losing an Islamic identity. It's not that they advocate a return to a golden era in the 7th Century, but that they advocate a return of Islam in modern life."
Filling a void
Today, Egypt is approaching the end of an era. No one knows for sure what will happen when President Hosni Mubarak, 82, is gone, or who will succeed him.
Against that backdrop, the Muslim Brotherhood is one of the most hotly debated issues.
So much so, that the first ever drama about the group has just hit Egyptian TV screens.
The drama's script writer, Wahid Hamed, is very critical of the Brotherhood.
"They are the organisation from under whose mantle all violent jihadi movements came," he says.
But he acknowledges that it can not be ignored, especially now.
"Egypt is waiting for salvation from entrenched corruption, unemployment, problems with its infrastructure, overpopulation, and countless other problems… And the alternative which presents itself strongly on the scene today is the Muslim Brotherhood," he says.
Magdi Abdelhadi's two-part documentary, The Brotherhood, can be heard on the Monday Documentary of the BBC World Service radio.