8 April 2018 . By Owen Amos, BBC News, Washington DC

For the first time in at least 100 years, the US Cabinet has a bible study group. What do they learn? What does Donald Trump make of it? And why aren't women allowed to teach? 

Every Wednesday, some of the world's most powerful people meet in a conference room in Washington DC to learn about God. 

The location can't be revealed - the Secret Service won't allow it - but the members can.

Vice-President Mike Pence. Secretary of State Mike Pompeo. Education Secretary Betsy DeVos. Energy Secretary Rick Perry. Attorney General Jeff Sessions. The list goes on.

In total, 10 cabinet members are "sponsors" of the group. Not everyone attends every meeting - they are busy people - but they go if they can.

Meetings last between 60 and 90 minutes, and members are free to contact the teacher after-hours. So who is the man leading the United States' most-influential bible study?

Step forward Ralph Drollinger, a seven-foot tall basketball pro turned pastor. Or, as the 63-year-old describes himself: "Just a jock with some bad knees."

Drollinger grew up in La Mesa, a suburb of San Diego, California. As a child, he rarely went to church - "Probably half a dozen times," he says - and didn't get far with the Bible.

"I always promised myself I'd read it," he says. "But every time I tried, it didn't make a whole lot of sense to me."

In his last year of high school, after a basketball game, some cheerleaders invited him to bible study. He went, and his world changed.

"It was the first time I really heard the gospel," he says. "So I went home, read through the whole gospel of Matthew that night, and asked Jesus into my heart."

In 1972, Drollinger went to the University of California in Los Angeles on a basketball scholarship. He attended a bible-teaching church and, over the next four years, "fell in love with the scriptures".

After college, he could have played pro basketball - he was picked in the NBA draft three times - but, each time, turned it down.

"I sensed such a passion for ministry that everything paled in comparison," he says.

Instead, he signed for a Christian team called Athletes in Action. They played basketball around the world - 35 countries, he reckons - and preached the gospel at half-time.

"That was kind of perfect for me," he says. "Because I really didn't like basketball - but I liked to preach."

Drollinger did eventually turn pro, signing for the Dallas Mavericks in 1980, but only because he wanted to attend the seminary there. He played six games in the NBA and left after one season.

After retiring from basketball he worked in sports ministries, before turning to politics in 1996. The road to the White House started with failing Christians in California.

In 1996, Drollinger's wife, Danielle, was executive director of a political action committee in California. It tried - in her words - to unseat liberals from the state legislature and get Christians elected.

"But she was frustrated," says Mr Dollinger. "They would send guys to California's capitol - and she was great at getting them elected - but they would soon lose their Christian moorings."

So they took over the existing ministry in Sacramento, changed the name, and offered weekly bible studies, support, prayer, and one-on-one ministry.

It proved "wildly successful", so they expanded. Capitol Ministries is now in 43 US state capitols, and more than 20 legislatures abroad.

Each class is led by a local pastor, but none is led by a woman. Why not?

"There's no [Biblical] prohibition of female leadership in commerce, there's no prohibition of female leadership in the state, and there's no prohibition of female leadership over children," says Drollinger.

"But there is a prohibition of female leadership in marriage, and female leadership in the church. And those are clear in scripture… it doesn't mean, in an egalitarian sense, that a woman is of lesser importance. It's just that they have different roles."

In 2010, Capitol Ministries arrived in Washington. There was already a ministry called The Fellowship, which runs the National Prayer Breakfast, but Drollinger felt it had "lost its marbles, Biblically".

It was, he says, candy floss Christianity - big, sweet, unsubstantial. By contrast, he wants to offer a "high-protein diet", teaching the bible book-by-book, one verse at a time. In Drollinger's studies, it can take a year to finish one book.

"If you don't have a spiritual coach that's really driving you in the word of God - and driving you toward holiness rather than your own sinful, latent nature, and your own depravity - then you're not going to grow into Christ's likeness," he says.

The Fellowship, he says, believes legislators can do bible study among themselves.

"I say no, technical foul. 'How will they hear without a preacher?' Romans 10:15."