Grey's Anatomy has been running now for 12 years and this week the hospital drama celebrates its 300th episode in the US, quite an achievement in today's fast-paced TV landscape.

The show has seen many characters come and go over the years but actress Ellen Pompeo, who plays Meredith Grey, has always remained its anchor, and according to Shonda Rhimes, it will stay the way.

Speaking to E! Online, the showrunner said, "Ellen and I have a pact that I'm going to do the show as long as she's going to do the show. So the show will exist as long as both of us want to do it.

"If she wants to stop, we're stopping. So I don't know if we'll see 600 [episodes], but I want to keep it feeling fresh.

"As long as there are fresh stories to tell and as long as we're both excited about the stories being told, we're in. So we'll see where that takes us."

The 300th episode, which hopefully will air this side of the pond soon enough, is set to include significant callbacks to original characters Cristina Yang (Sandra Oh), Izzie Stevens (Katherine Heigl), and George O'Malley (TR Knight), as a freak rollercoaster accident brings three new patients to Grey Sloan Memorial Hospital.