With 100 caps for Wales and captaining the British and Irish Lions, his rugby career and achievements are up there with the greatest. More recently however Gareth is better known through his TV and media career and his campaigning, particularly for the LGBTQ+ community and for people living with HIV.

Gareth came out as gay in 2009, the first openly gay professional rugby union player to do so, and the next year was voted the most influential gay person in the UK (Independent on Sunday Pink List). In 2019 Gareth announced he was HIV positive, and since then has worked tirelessly to remove the stigma surrounding the virus and to help others with the prejudice associated with HIV.

Gareth launched the Tackle HIV campaign in 2020 with ViiV Healthcare, with The Terrence Higgins Trust as the charity partner.