The lavish 2,400 sq ft illegal basement lying underneath the Kowloon Tong home of former chief secretary Henry Tang Ying-yen was most probably built at the same time as the house, a court heard yesterday.
Prosecutor Keith Oderberg said that "when we applied common sense" to think of the whole matter, the construction of the basement was likely to have preceded the issuing of the occupation permit for the house in 2007.
"The prosecution case is all about timing. We have to consider when it happened," Oderberg told Kowloon City Court.
"It is very unlikely that the illegal construction was carried out after the house was erected."
He said it would have been "silly" and "absurd" to conduct more massive works after all the main construction was done, as that would have again involved the movement of hundreds of trucks and machinery around the premises.
The prosecution was seeking to dismiss defence arguments last week that the notorious basement that derailed Tang's shot at becoming chief executive in 2012 could only have been added after the permit was issued and the defendants' involvement in the work had ceased.
The court heard testimony from structural engineers that it was technically impossible for the underground area to have been excavated between October 10 and 24, 2005, and then hidden from planning inspectors.
Architect Henry Ho Chung-yi, engineer Wong Pak-lam and contractor Hien Lee Engineering are each charged with one count of building without planning approval between 2005 and 2007 and one count of knowingly misrepresenting information to the Building Authority.
All three defendants were involved in building the house at 7 York Road. Tang's wife Lisa Kuo Yu-chin contacted a consultancy to redevelop the house in 2002, the court heard earlier. An occupation permit was obtained from the authority in January 2007.
No basement was incorporated in the initial building plans.
Surveyors who inspected the works might not have pointed out the illegal structures as they knew the owner could apply for approval to the change of plans any time, the prosecutor said in his final submission.
The three defendants deny having worked on or known about the basement before their work was completed in 2007.
They say the basement was added by partially demolishing finished slabs after the building was completed in compliance with approved plans.
In November, Kuo was fined HK$110,000 after pleading guilty to starting the basement's construction without approval.
The defence lawyers will deliver their final submissions before acting Chief Magistrate Clement Lee Hing-nin today.