James Van Der Beek has dropped out of the Dawson's Creek reunion after being struck down with "two stomach viruses "

He explained the decision in a message posted on Instagram, writing: "This is the evening I'd been looking forward to MOST since my angel Michelle Williams said she was putting it together, way back in January ...

"So you can imagine how gutted I was when two stomach viruses conspired to knock me out of commission and keep me grounded at the worst possible moment.

"Despite every effort ... I won't get to be there. I won't get to stand on that stage and thank every soul in the theater for showing up for me, and against cancer, when I needed it most."

The event will still go ahead with cast members Michelle Williams, Katie Holmes and Joshua Jackson - and James will be replaced by Hamilton creator Lin-Manuel Miranda, who will take on the part of Dawson Leery for the table read.

James went on to add: "I DO have an understudy. A ridiculously overqualified replacement who would have been #1 on my wishlist (had I ever dreamed he'd be available). Someone my kids would definitely consider an upgrade over me ... Plus, he already knows how to get to the theater. So that's convenient.

"The role of Dawson, usually played by James Van Der Beek ... Will be played by Lin-Manuel Miranda. Can't believe I just got to type that.

"Everyone please enjoy all the love in that room. Shine some on my family. I will be beaming and receiving from afar in a bed in Austin.

"And thank you @lin_manuel. You were a hero to my kids before ... now you're a demigod."

Fellow cast members Mary Beth Peil, John Wesley Shipp, Mary-Margaret Humes, Nina Repeta, Kerr Smith, Meredith Monroe, and Busy Philipps will also be part of the reunion.

Kerr, Meredith and Busy all joined the show after the first season, so will read various other roles instead of appearing as their own characters.

Jason Moore, one of the show's original directors, will take the reins on the reading, while Michelle, her husband Thomas Kail, and Dawson's Creek creator Kevin Williamson are among the producers.

My Week with Marilyn star Michelle - who played Jen Lindley - said in a statement: "We grew up in Capeside and that's a bond that will last a lifetime. We wanted to gather around our dear friend James and remind him that we are all here.

"We always have been and we always will be. And I know the fans of Dawson's Creek feel the same way."

Creator Kevin added in his own statement: "I am so excited to reunite with James, Michelle, Katie, Joshua, and our Dawson's Creek family for such a special night. Dawson's Creek changed my life.

"What began as a personal story about a young man and his friends navigating their way through the challenges of life became so much more than I ever dreamed.

"It created an enduring fandom and legacy all over the world. I am so honoured to be a part of it and to support our beautiful friend, James, as we continue to navigate our way through life and its many challenges."