Lansdown began his association with City in 1996 when he joined the board.
In October 2002 he took over from John Laycock as chairman.
Less than a year later City lifted the LDV Vans Trophy at the Millennium Stadium, Cardiff, after beating Carlisle United 2-0.
However, City were beaten in the play-offs in 2003 and 2004 - the latter in the final against Brighton & Hove Albion back in Cardiff.
Lansdown dearly wanted to return City to the second tier, which arrived in 2006/07 when Gary Johnson's side finished runners-up to Scunthorpe United to secure automatic promotion.
A year later City were just one game from the Premier League as they took on Hull City at Wembley in the Championship play-off final. In front of more than 86,000, City were beaten 1-0 through Dean Windass' first-half strike.
Lansdown stepped down as chairman in 2011, leaving the board, but remaining the club's owner.
Another of his ambitions was to ensure City had a stadium to be proud of, initially looking to build a brand-new venue in Ashton Vale.
When that project hit the buffers, he turned his attentions to a £45m redevelopment of Ashton Gate into a 27,000-seater stadium.
That began in 2014, just as the team embarked on a double-winning campaign - lifting the Johnstone's Paint Trophy at Wembley and the Sky Bet Championship title with 99 points.
The giant new West Stand has been named the Lansdown Stand in his honour.
Lansdown lives in Guernsey but still attends the vast majority of games with his wife Maggie.