The four - who were all team mates during their time at Kilmarnock in the late 1990s - are undertaking the quest to raise money for Rett Syndrome Research Trust UK. It's a cause close to their hearts as Mark's three-year-old daughter Dionne has Rett Syndrome.
The former Saints, together with a number of other people, will attempt to climb Ben Nevis, Scafell Pike and Mount Snowdon in the space of 24 hours. Anyone looking to sponsor them in their efforts can visit http://www.justgiving.com/Mark-Reilly or http://www.justgiving.com/kevin-mcgowne - and make sure you click for Gift Aid to be reclaimed.
Mitchell briefly played for Saints in 2003 while Reilly, Millen and McGowne were all part of the Saints double winning side of the 2005/06 season. Reilly retired at the end of that season while McGowne stayed for another season before going on to assist Jim Weir - who is also doing the challenge - at Montrose and Brechin. Millen was still playing for the first team in 2008 and continued to assist manager Gus MacPherson until 2010. The pair now form the management team at Queen of the South.