He said he did not have a new job lined up and had resigned because he had 'been through the whole cycle' of comms roles at Standard Life and felt it was 'time for a change'.
Arthur, who has spent 16 years working in investment management and latterly coordinated Standard Life's independent financial advisers in the South-East, became director of corporate affairs in 1999.
One of his first tasks was to handle comms around Standard Life's 1999 AGM, when Monaco-based private investor Fred Woollard led a campaign to demutualise the company.
While a mere 50 people attended Standard Life's AGM in 1999, around 1,100 people attended last year.
The company's corporate affairs function has also grown under Arthur's stewardship. A team of 32 Standard Life staff now work in internal comms, media relations, public affairs, event management, and technical support for the company's intranet site.
Finance director Alison Reed, who joined from Marks & Spencer last June, has since taken responsibility for the investor relations function, which Arthur set up in 2004.
Meanwhile, Standard Life is on the hunt for a director of investor relations following the departure of Amanda Forsyth last November after 18 months.
The company is set to announce the date of a policyholders' meeting to vote on demutualisation this week.
At the meeting 2.4 million policyholders will be asked to approve the listing of the company.