The contemporary take on the classic Alexandre Dumas characters had a consolidated audience of 9.3 million for episode one, which aired on Sunday 19th January, making it the corporation's biggest new drama launch since Call The Midwife in January 2012. The first three episodes have averaged 6.3 million viewers in the overnight ratings.
Set on the streets of 17th-century Paris, where law and order is more an idea than reality, the series follows the eponymous quartet who are far more than King Louis XIII's personal bodyguards, but ultimately stand resolutely for social justice: for honour, valour, love - and for the thrill of it.
It stars Luke Pasqualino as D'Artagnan alongside Tom Burke as Athos, Santiago Cabrera as Aramis and Howard Charles as Porthos. All four will return in series two, whose length is yet to be confirmed.
Creator Adrian Hodges said:
Kate Harwood, the head of Drama England at BBC Drama Production, said:
Episode four - entitled The Good Soldier - airs at 9pm tonight.
Guest actors still to come in this series include Sean Pertwee, JJ Field, Vincent Regan, Ashley Walters, Amy Nuttall, Tara Fitzgerald, Annabelle Wallis, Zoe Tapper and Vinnie Jones.