Police think Anthony and Linda O’Malley may have been held prisoner for up to a fortnight while they were forced to hand over thousands of pounds.
The news has confirmed the worst fears of the couple’s daughter, Nicola Welch from Fleet, who held a series of press conferences after her parents went missing in September.
Detectives think Mr O’Malley, 42, and his 55-year-old wife may have fallen victim to a property scam by practised fraudsters who turned violent.
They believe Mrs O’Malley, a store manager, was imprisoned in a tiny cellar of a villa while her husband, a self-employed car salesman, was taken at gunpoint to withdraw money from cash machines.
On one occasion Mr O’Malley was made to withdraw £18,000 in cash from an account the couple had opened at a Spanish bank.
In total the men took £25,000, but when the O’Malleys’ cash card was stopped by their bank in north Wales they were killed.
Local police, working with officers in Wales, discovered the couple’s rented Fiat Stylo at El Saler, six miles south of Valencia.
The number plate had been changed but they followed the driver back to a nearby apartment before arresting him and his brother-in-law.
They found a string of documents linking them to the O’Malleys, including their passports and bank cards.
Fears the couple may have been tortured emerged following reports that a truncheon and electric prod were found in a flat belonging to one of the men.
Police showed a news conference a video of one of the handcuffed suspects leading them to the tiny cellar.
A thick layer of concrete had been poured over it and a window had recently been bricked up.
The Venezuelan men, aged 53 and 37, had rented the mountain villa — in the El Baradello area of Alcoy, an industrial town 12 miles inland from Benidorm — with their wives and three children.
Officers used pneumatic drills and spades to dig through the concrete to a two by four metre hole where the bodies lay. One police chief admitted that if they had not been led to the spot the bodies would never have been found.
Juan Cortina, the Commissioner for Valencia, said the two suspects were professional criminals who had advertised the villa for sale in the English-language newspaper Costa Blanca News at a knockdown price.
The investigation into the deaths will now be passed to three judges and is expected to take some months.
Mr O’Malley’s brother Bernard, a 54-year-old builder from Widnes, described the discovery of the bodies as “sickening”.
“It’s been sheer hell waiting to hear what happened to them,” he said.
“As the weeks and months passed we knew something bad had happened. But we were hoping against hope that they might still be alive and well.
“It is horrible to think about how they were killed.
“For a long time they had been talking about and planning a move to Spain.
“They were always looking in estate agents’ windows when they were out there.
“They had their hearts set on a nice villa away from the hustle and bustle of tourist resorts.
“They wanted to get in touch with the real Spain in a rural village where they could settle down and enjoy a long retirement.
“But that dream and their lives have been snatched away from them.”