WATCH: Rap battle between Big Narstie and Lady Leshurr for Big Mac 50th anniversary

They're inviting people to share their own Big Mac bars.

McDonald's is launching the 'Grand Big Mac', as well as the 'Mac Jr.', here in the UK tomorrow to celebrate the Big Mac's 50th anniversary. And as part of the launch Big Narstie and Lady Leshurr have battled it out, each trying to rhyme off the list of ingredients, from the 1974 Big Mac advert, as quickly and creatively as possible - in freestyling that is as hilarious as it is ingenious. Watch a clip of them here: https://www.youtube.com/watch?v=MllrfG0PidA Fans of the Big Mac can get involved in the birthday celebrations on social media using #BigMac50, to show off their lyricist and vocal skills. As for the burgers, the difference compared to a standard Big Mac is purely the size. And is described by Maccies itself as follow:

• New and limited-edition Mac Jr.: Made with the all same iconic ingredients (with one less patty), the Mac Jr. is smaller than a Big Mac, but still packs a pickle.
• New and limited-edition Grand Big Mac™: With the same Big Mac® much loved ingredients, the Grand Big Mac™ offers the one-of-a-kind taste you love in a larger size.

I can't be the only one who can't wait to devour one of them.