A man killed his adopted son by hitting him over the head with a scaffolding pole then made a bungled attempt to dispose of his body in the River Thames, a court has heard.
Retired fireman Colin McSweeny is on trial at the Old Bailey accused of murdering son Shaun at the family home in Thornton Heath, south London, on November 20 last year.
Afterwards, he entertained a female police officer who had dropped by to see his wife by making tea and regaling her with amusing anecdotes of his time as a Scout leader, the court heard.
McSweeny, 59, was caught by police after he was spotted in the early hours of the morning trying - and failing - to drop the body into the Thames at Deptford Wharf while the "tide was against him".
Opening the case, prosecutor Crispin Aylett QC told jurors the murder was "as deliberate as it was desperate".
He said McSweeny killed his son because he was getting in the way of his and his wife Gloria's hopes to take custody of a young child, who cannot be identified for legal reasons.
On the night of the murder, 24-year-old Shaun bought a kebab after work and sat in his van eating it outside the home where he lived with his parents.
The defendant allegedly lured him into the garage and repeatedly hit him over the head from behind with a scaffolding pole, fracturing his skull.
When police searched the garage, they found the weapon wrapped in cling film as well as a tarpaulin which had been laid on the floor.
After killing Shaun, McSweeny moved his son's work van from outside the house to about half a mile away so the police officer friend - who was due to visit - did not spot it.
Sarah Lavington had gone to the house in Parry Road with flowers and chocolates to celebrate Mrs McSweeny's 60th birthday a couple of days earlier.
Mr Aylett said: "What followed can only really be described as surreal - while Shaun's body lay in the defendant's garage, he and his wife entertained a police officer in their living room."
McSweeny made the visitor a cup of tea and he and his wife sat chatting and told her funny stories for a couple of hours, the court heard.
When Mrs Lavington made to leave at 11.15pm, Mrs McSweeny said she had no idea where Shaun was, saying he would probably come home drunk and "tread mud all the way up the stairs".
Mr Aylett said: "The defendant, of course, would have known only too well where Shaun was. Now he had to get his body out of his garage."
Shaun's van was driven further away from the house from its temporary hiding place to around a mile and a half from Parry Road as the crow flies.
Some time after 2.30am, a man in a flat overlooking Deptford Wharf saw a large black car pulling up.
The witness said a white-haired man got out and opened and shut the boot before driving off, and s hortly afterwards he returned and dragged what looked like a body by the ankles.
The man was said to have returned to the car to retrieve a piece of tarpaulin and went back to where he apparently left the body and dragged it to the wall alongside the waterfront.
The witness said that when the man tried to lift the object over the wall, it was clear it was a body, and he called police just before 3am to report it.
Before he got off the phone, the driver had dragged the body back to the car and driven off.
Mr Aylett said: "It would seem that the tide must have been against the defendant."
En route to the scene, Inspector Simon James saw a black 4x4 vehicle going in the opposite direction and went in pursuit.
After the car was stopped by police in Evelyn Street, Deptford, the defendant was asked by an officer if he knew why he had been stopped.
He replied: "Yes."
He was then asked: "What have you got in the car?"
He replied: "A body."
Officers uncovered Shaun's body lying on a heavily-bloodstained tarpaulin in the boot.
When asked if anyone else had come to harm, McSweeny said: "No, there's only one body you have to worry about."
A search of Deptford Wharf uncovered blood traces on the wall, a piece of tarpaulin, one of Shaun's shoes and a trail of coins and buttons along the route his body had been dragged.
Mr Aylett told jurors the defendant would say that he acted in self-defence after being pushed by Shaun in the garage where he had gone to pick up some golf clubs.
But the lawyer said: "Instead, the prosecution allege that the defendant killed his son deliberately. It may have been hastily conceived and ill-thought through but it was, nonetheless, done deliberately.
"Having murdered his son, the defendant intended to dispose of his body in such a way as might mean that it was never found or if it was, that Shaun's death could not be linked to him. In the event, of course, getting rid of the body turned out to be rather more difficult than he had imagined and the plan quickly unravelled."
McSweeney denies murdering Autoglass repairman Shaun.
The trial was adjourned for the day.