Lyness was initially brought to Paisley by Oran Kearney in September 2018 to help address the staggering squad deficiencies left by Alan Stubbs after the former Hibs boss disastrous three months at the club left newly promoted Saints odds on favourites to return to the second tier.

Serving as the third choice keeper behind Craig Samson and the on loan Danny Rogers, the Birmingham born shot stopper soon found himself as number one at the club in December of that year after 2013 League Cup winning custodian Samson dramatically left the club in November to take a coaching role at Sunderland with Jack Ross, and then Rogers found the Premiership too high a standard after he stepped in to the number one position, allowing Lyness to appear in the last four league matches before the winter break, where he performed well in a struggling side.

When the transfer window opened in January 2019 however, Kearney decided to sign Vaclav Hladky as his first-choice goalkeeper with Jordan Holmes arriving on loan from Bournemouth, permitting Lyness to leave the club at the end of his 3-month deal on the 7th January 2019 and join Raith Rovers for the rest of the season.

The former Blackpool and Burton Albion keeper had done enough to impress Kearney though, and Lyness agreed to return to Saints in the summer of 2019 as back up to the now cult hero Hladky. Before pre-season training started however, Kearney left the club and was replaced by Jim Goodwin who kept the Englishman as number two for several seasons under the Czech keeper and then Jak Alnwick, until Lyness was finally required in February 2021 after the latter was sent off against Hibs in Paisley, when Lyness made his second debut for the club, the first of nine appearances he would make in his second spell.

Highlight of his Saints career however would be on a cold pre-Christmas night at Paisley in late 2021 when the SPFL ordered a seriously COVID hit home side to take on Celtic despite having only a couple of first team players available. During an astonishing 90 minutes, Lyness denied Celtic time and time again with some remarkable goalkeeping to help gain Saints an invaluable point after a 0-0 draw.

The popular Englishman made a further four appearances for the club later that season after Stephen Robinson took over, but was released on the 6^th October 2022 having dropped back down to third choice keeper following the emergence of Peter Urminsky from the under 20 squad. Lyness signed for League One Airdrie the following day.