SJP has recently been under fire, particularly from national media, for its charges and sales incentives for staff.
Dame Helena stepped down recently from her role as head of personal investing at Legal & General Investment Management after two years in the post. Before L&G she was chief executive of Newton Investment Management from 2001 to 2016, a company she joined in 1984.
Until recent years she was one of the few women to hold a chief executive role in investment management. She is a long term campaigner for better representation for women and founded The 30% Club nearly 10 years ago to campaign for greater female representation on company boards. The campaign has gone global.
Iain Cornish, chair of St James's Place, said: "I am delighted that Helena is joining the board of St. James's Place. Her expertise in financial services, insight into investment management and experience of running a major asset management company will be of great value to the board.
"As I said earlier this year, attracting and developing a diverse range of talent at St James's Place is a priority for the board. While I am pleased that Helena's appointment takes the proportion of women on our board to a third, there is always more to do in relation to inclusion and diversity across the business, and we will continue to make progress on this."
Dame Helena said: "St James's Place has been a huge success story in terms of growth and the provision of excellent service to its clients over the past three decades. The board's strategic priorities include continuing to improve important matters such as culture, inclusion and diversity, and I look forward to using the experience and insights I have gained throughout my career to help the company do this."
• Editor's Note: In an earlier version of this story today Dame Helena's surname was mis-spelt. Apologies to her and our readers.