Dylan Hartley reported concussion symptoms after England's loss to Ireland

England captain Dylan Hartley has yet to come through return-to-play protocols after reporting concussion symptoms following last month's Six Nations defeat to Ireland, and his Northampton club coach is reluctant to put a timeframe on his return.

News of Hartley's concussion issues will be a worry for England coach Eddie Jones, who will be keen to have the hooker available for a three-Test series against South Africa in June.

"Dylan reported concussion symptoms after the Ireland game so it's one of those he'll go through the return-to-play protocols," Saints coach Alan Dickens told reporters.

"In terms of the focus on concussion now, it's a concern for all the players. That's why they're so stringent in terms of the process to return to play. We'll do what's right by Dylan."

Hartley, who has missed Northampton's last two matches, was sidelined for a significant spell two years ago due to head injuries.