Tonight Benedict Cumberbatch takes on Daniel Radcliffe as the new series of Sherlock and the final instalment of the Harry Potter saga go head to head on BBC1 and ITV. Both franchises have huge fan followings as well as a major wider audience appeal.
The Deathly Hallows Part 2 at 8pm will be the first free-to-air showing of the conclusion to the seven-movie Harry Potter saga, while an hour later the long-awaited opener of Sherlock series three will finally reveal how the detective faked his death when he jumped from the roof of St Bart’s Hospital.
Of course, scheduling clashes don't have quite the same significance they once did – anyone with a set-top recorder can watch both. But just as Saturday night talent show rivals The X Factor and Strictly Come Dancing are judged on their overnight viewing figures it will be interesting to see how Sherlock fares against Harry Potter.
The final measure of how many people see them will come when the consolidated figures are released, taking into account those who've recorded them and watched in the following week as well as on the day. But there's still a battle to be won on the night.
One factor that might play in Harry's favour is that, due to rights issues, The Deathly Hallows will not be available on catch-up service ITV Player, while Sherlock will be up on BBC iPlayer almost immediately after it airs. So anyone who can't record Harry Potter will miss it (even watching on ITV+1 won't make a difference as they will still overlap) but they can watch Sherlock right after the movie finishes.
Twitter could play a big part too. You might think Sherlock will have the edge there – having waited so long for a solution, fans will be bursting to share their thoughts online – but you can't underestimate how much a first Freeview showing of Deathly Hallows 2 will have people talking. Both are event TV.
What exactly will happen when the boy wizard meets the great detective? We'll just have to watch and see.
Harry Potter and the Deathly Hallows Part 2 is on ITV at 8pm. Sherlock is on BBC1 at 9pm