Ed Sheeran's cousin expects him to peak in his mid-40s.

Murray Cummings has dedicated the past eight years to producing a documentary based on his famous relative called 'Songwriter', and after doing his research and judging the 'Perfect' hitmaker's idols' longevity, he expects Ed to continue to mature as a writer for the next 18 years or so.

Speaking to the Daily Star newspaper: he said: ''I can't wait to hear what he does next. Because I know his musical influences and that he grew up on Bob Dylan and Van Morrison, I really want to hear the album that he makes at 45.

''Maybe it is the commercial peak now but it is definitely not the songwriting peak.''

The film, which has been bought by Apple, will follow the 27-year-old singer's early busking days right up to his record-breaking hit song 'Shape of You', and is set to reveal his secrets to making chart-topping hits.

Murray explained: ''I always felt my documentary about him would be about him doing small gigs but then he became Ed Sheeran.

''So I thought, 'What original take could I do that only I could do?' And my passion when he was working was watching him make a song.''

Ed is so prolific with his writing that his cousin almost missed getting footage of him doing 'Shape of You' last year, despite recording for around 70 hours.

He recalled: ''I had already packed up and come home then he just sent me an email saying, 'Wrote a new song'. Then I was like, 'Oh no! I don't have any footage and Ed is going to make it a single'.

''Luckily he was still to mix it and Ed re-wrote quite a lot of stuff in that mix, so we got that, which gave us a different stage to the process.

''There are a few scenes where he didn't know that the camera was running.''