[1] He is nicknamed The Horse due to his long, powerful strides, which resemble a gallop as he sprints down the wing.

[citation needed] Muir holds a degree in mechanical engineering from Northumbria University, which he represented in the BUCS Super Rugby competition.

He made his debut for England in the Assupol International Sevens tournament in South Africa in 2017.

[3] In 2019 Muir was named England Sevens Player of the Year, the first person to do so in their debut season.

[7] On 23 January 2024, Muir received his first call-up to the senior England squad by coach Steve Borthwick for their Six Nations campaign.