They are former collaborators, arch-rivals, one-time enemies and responsible for one of the best r'n'b songs of all time.

So when Brandy and Monica teamed up for a song battle on Verzuz last night, it's no wonder that it attracted over a million viewers.

The pair, of course, are the singers of 'The Boy is Mine', but their relationship hasn't always been plain sailing after they fell out despite the 1998 song's huge success.

Verzuz, if you didn't know, is an Instagram Live 'show' created by producers Timbaland and Swizz Beats. It pits two well-known musicians against each other in a head-to-head battle to basically see who has the better back catalogue. Brandy and Monica's battle broke records, with over 1.2 million viewers tuning in.

While there was some tension between the pair at times, the vibe was mostly one of respect - and even US Vice-Presidential nominee Kamala Harris made a cameo via a screen in the studio, encouraging people to vote.

Adele, Mariah Carey and many other stars also tuned in and left comments.

The battle ran for 20 rounds - and although there was no official 'winner' declared, many decided that Brandy had come up trumps. In fairness, Monica's lack of enthusiasm in singing their final song 'The Boy is Mine' didn't help her cause.

You can watch the whole thing below:

And if you don't have time for the whole thing, here's 'The Boy is Mine':