Sanjay Nijhawan, 46, was struggling to cope after quitting his highly paid job with Barclays, a court heard.
The crisis came to a head when his wife Sonita, 38, asked for a divorce. Nijhawan stabbed her repeatedly in the head and neck before slitting her throat.
He was found sitting beside her body by worried family members who came to their luxury, gated property in Weybridge, Surrey.
Opening the case, prosecutor Sally O'Neill said his defence was expected to be that he had an abnormality of mental function at the time "which substantially impaired his ability to form a rational judgement or exercise self control."
The jury heard that after he was arrested by police, Nijhawan told officers that he had become "deranged" and had suffered a nervous breakdown.
Ms O'Neill said: "The number and nature of her cuts make it clear that she was the victim of a fatal and sustained attack.
"She had a very large number of cut and stab injuries to her neck and head.
"Underneath her body was an axe. He (Nijhawan) was sitting on the kitchen floor next to her body repeatedly stabbing himself to the legs with a small knife.
"Sonita had 124 significant injuries to her body including 40 cut and blunt force injuries to her head, of which 18 were to the back of the head, 11 to the side and 10 to the left hand side of her skull.
"These were all likely to be caused by an axe.
"There were 25 stab wounds to left side of her neck, more likely to have been caused by a knife. The defendant was immediately taken St George's Hospital in Tooting."
The cause of death was neck and head injuries, said the prosecuter.
Ms O'Neill said Nijhawan made Google searches before the killing on how to commit suicide and on how to identify the "soft parts of a female human skull."
The jury was told that family relatives rushed to the mansion home after Nijhawan made bizarre phone calls and sent text messages about keys to the house.
Ms O'Neill said the husband had taken away his wife's mobile phone, even though she was on call 24-7 as a director of two care homes run by her family.
Jurors heard he claimed he took away the phone so his wife could not tell family members about the divorce discussion before a family event on the upcoming weekend.
The court also heard that police seized a note from Nijhawan which he wrote in hospital and which stated: "I would like to issue a statement immediately offering my severe remorse.
"The mindless act has lost the life of a beautiful and amazing woman.
"I have failed in my duty as a son-in-law and a brother."
Ms O'Neill told jurors: "It seems that in the preceding months leading up to this event Sanjay Nijhawan began to suffer from stress and anxiety partly as a result of his job and he was finding it very difficult to cope.
"He also felt under financial pressure because of the move to the house although it is not clear exactly why this was as both of the family were wealthy."
The trial continues.