A 23-year-old man from Southampton has been arrested on suspicion of murder.
A 27-year-old woman from Gosport was re-arrested on suspicion of assisting an offender after new information came to light.
A 49-year-old man from Southampton and a 33-year-old man from Southampton have also been arrested on suspicion of assisting an offender.
All four people remain in custody at this time.
Whilst officers arrested a 47-year-old Southampton woman on suspicion of assisting an offender on Thursday (23 March); she was subsequently bailed while enquiries continue.
Mark, 64, died of a stab wound to his chest at his home address in Warburton Road, Southampton, on 25 February.
Anyone with information can call 101 or report via the police website, quoting Operation Hibiscus or the crime reference number 44230077698.
Alternatively, you can contact the independent charity, Crimestoppers, anonymously on 0800 555 111, or via their online form.
