[3] Barnes attended Hutton Grammar School prior to going to University of Cambridge where he completed his MA in law and archaeology at Selwyn College in 1981.

He is an Associate of the Chartered Institute of Bankers (UK) and attended Harvard Business School's Program for Management Development in 1992.

[4] He spent 20 years in Australia, floating realestate.com.au on the ASX in 1999[5] and holding senior roles in companies including Macquarie Bank, Citi, Tower, and County Natwest, and was chairman of Australasian Wealth Investments.

[10][11] In late March 2018, Barnes said that the trial was going well with staff reporting more time for family, hobbies, ploughing through to-do lists and home maintenance.

[46] Barnes recommended to the Perpetual Guardian board that the four day work week program[47] continue,[48][49] and it has since been rolled out on a permanent basis.

[67] In July 2018 he appeared on the Kiwi big business podcast, High Altitude, hosted by John Peebles, discussing innovation, change management, philanthropy, entrepreneurship, the military, leadership, team engagement and the four day workweek initiative.

[80] By the time Barnes' book 'The 4 Day Week: How the flexible work revolution can increase productivity, profitability and well-being, and create a sustainable future' was published in January 2020,[81][82] the initiative had won several global awards.

[83] The four-day week again emerged as a prominent global talking point amid the COVID-19 pandemic, with lockdowns in many countries forcing millions of people to work from home.

"[84] Her comments spurred a fresh wave of global media coverage[85][86][87][88] of the four-day week as part of a future of work where the trend is moving away from large centralised office hubs in downtown metropolitan areas.

[90][91] Under Barnes' leadership, Perpetual Guardian provided sponsorship for a program which sees 3500 children from rural or low decile schools to visit Otago Museum's planetarium each year in an attempt to encourage youngsters to become interested in science and technology.

In April 2020, when the RSA's annual Poppy Appeal had to be postponed due to COVID-19, Barnes stepped in to create a virtual solution to help raise funds.