Frederick Bartman, 68 - who played Dr Simon Forrester in the 1960s television series Emergency Ward 10 - struck Lady Brenda Cross, 73, between 30 and 40 times with his fists, feet and the fire irons, it was alleged.
David Calvert-Smith, for the prosecution, said the attack took place in September 1991 in the basement of the shop, Anno Domini, in Pimlico, south-west London, owned by Mr Bartman and his partner, David Cohen. It followed an argument between Mr Bartman and Lady Cross, who had worked part-time at the shop for several years.
Mr Bartman, of Chelsea, described as a man of good character and a 'successful professsional actor', denies murder.
The court was told that the shop had opened in 1976, but by 1991 the business was doing badly.
Mr Calvert-Smith said a pathologist's report concluded Lady Cross had been knocked or pushed to the ground. One of the fire irons had been used to beat her and she had lost consciousness.
Some time elapsed, during which she bled profusely and it was possible she regained consciousness, which may have prompted the 'second terrible attack'. Her injuries included three fractures of the skull.
Lady Cross was found after her husband, retired Air Chief Marshall Sir Kenneth Cross, went to collect her from the shop. She was still alive, but died of a heart attack as ambulance crews attempted to revive her.
Witnesses said that when Mr Bartman arrived at the scene, he looked ashen, was shaking, and kept saying 'she's dead, isn't she?'
Mr Calvert-Smith said police were unable to find any evidence of theft or intrusion at the shop or of a sexual attack. Lady Cross was a 'a much loved woman with no known enemies'.
Mr Bartman was not an initial suspect and in statements to police said he had spent the morning at his home. Suspicion fell on him after police obtained evidence from witnesses that he had been outside the shop on the morning of the murder and his car had been parked near by.
The trial continues today.