Artemis’ senior partner, Mark Tyndall, said the hires would allow the firm to offer its clients a dedicated North American equity proposition
He commented: 'Our strategy for meeting our clients’ needs continues. With successful launches over the past three years of Global Income, European Opportunities and Global Select funds, complementing our established funds, we have already broadened what we offer our clients. Cormac and Stephen will allow us to add North American equities to our range for the first time.
'The investment records of Cormac and Stephen speak for themselves, as does the scale of the assets they manage. So we will all be very pleased to welcome them to Artemis.'
Sobin, who has 28 years' experience in US equities, joined the firm in September 2011 from Columbia Management - a subsidiary of Threadneedle's parent Ameriprise.
As part of the restructure Threadneedle will increase collaboration with Columbia Management’s US equities team.
Weldon has spent 17 years at Threadneedle, where he has carved out a reputation as a top US equity manager.
He took control of the Threadneedle American Select fund in December 2001 and over the last 10 years the fund has returned 134.5% versus a 118% rise in the S&P 500, making it the seventh best performer in a 56-strong peer group over this period.
Meanwhile Citywire AA-rated Stephen Moore is widely seen as one of the rising stars of fund management. This is demonstrated in the performance of his Threadneedle American Extended Alpha fund, which has returned 52% in the three years to the end of December versus an average return of 20.26% in its Alternative Ucits long/short equity peer group.
'Cormac has decided to leave Threadneedle after 17 years and we wish him well and thank him for his valuable contribution to the firm,' Threadneedle investment chief Mark Burgess said.
'Following his departure, we will continue to invest in our London team under Diane’s leadership, while also better and more fully utilising the research resources of Columbia Management.'
The Threadneedle US equity team will be boosted by the arrival of Nadia Grant, who joins from JP Morgan Asset Management and will assume control of the Threadneedle American fund.
Kochar, who has nine years' experience, joined Threadneedle in 2008, while Robson joined the firm three years later and is armed with 25 years' experience.
Threadneedle chief executive Campbell Fleming said: 'I am grateful for Cormac’s contribution to Threadneedle’s success and wish him well. Looking ahead, there is an exciting opportunity to increase collaboration with our Columbia colleagues and offer our clients a significantly enhanced US equities capability and we look forward to continuing to focus on delivering strong results for clients.
'The extensive additional resources and expertise available to our US equities team will provide added depth to our overall offering, and given Diane’s experience and expertise I am confident we will fully leverage this for the benefit of our clients.'