If it weren’t enough to do charity work, write a book and embark on a rockstar-style speaking tour, Michelle Obama has just added another string to her substantial bow.

Marriage celebrant.

Mrs Obama stepped forward this weekend to help a young couple tie the knot in a ceremony in their – and her – home town of Chicago.

Stephanie Rivkin and Joel Sircus were married at Theatre on the Lake in Chicago, where Mrs Obama led the couple through their wedding vows.

The couple had clearly called in a few handy connections to swing the former first lady frocking up and turning up.

Ms Rivkin is the daughter of Robert Rivkin, who is Chicago’s deputy mayor, and Cindy Moelis, who is president of the charity organisation,  the Pritzker Traubert Foundation. That is the Chicago-based charity of Penny Pritzker, a commerce secretary in the Obama administration and a long-time friend of the Obamas. She was also one of then president Barack Obama’s major financial donors.

In a rather lengthy wedding notice in The New York Times, Ms Rivkin and Mr Sircus made no mention of Mrs Obama’s turn, only the contributions of Universal Life Minister Robert M. Dresser, and Meredith H. Potter, a friend of the couple.

The couple met in high school and both graduated from Yale University, according to The Times.

Rockstar-style book tour

Meanwhile, Mrs Obama is selling out large-scale venues for an upcoming speaking tour to promote her highly anticipated memoir, Becoming.

I’m done with my book! I’ve learned a lot about myself and I’d like to share my story of BECOMING—the plainness, the blemishes, the crazy turns—with you on my book tour, beginning 11/13 in Chicago. Go to https://t.co/dVXmPri4OS to find out how to get tickets. #IAmBecoming pic.twitter.com/jmlbh19RXG

— Michelle Obama (@MichelleObama) September 12, 2018

The tour is filling venues with seating capacities of 15,000 and higher, usually reserved for sports events and rock concerts. Event organisers Live Nation last week had to add two events, at the Barclays Centre in New York City and the Capitol One Arena in Washington, to meet demand for tickets.

The book has already hit the top 10 on Amazon.com, almost two months ahead of its release date of November. The New York Times reports it seems to be “a guaranteed million-seller”.

“A memoir by a popular first lady with an international following and a relatively limited history of discussing her private life, especially her eight years in the White House,” The Times reported.

Live Nation said it booked the mega-venues because it knew the demand for Mrs Obama’s tour would be “extraordinary”.

But some of the tickets don’t come cheap. Prices range from just under $US30 ($41) to VIP tickets for $US3000 ($4100) – although the latter do include the chance to meet Mrs Obama.