Two members of the Antiquities Advisory Board expressed shock that the construction work had started and the wall, which stands almost three metres high, was about to go. Girders have been erected at the front of the site and foundation work for the auditorium has begun.

The 1906 church, itself a proposed grade one historic site and the oldest church in Kowloon, sits on raised ground, tucked away behind the wall and hidden from the bustle of Nathan Road by a number of banyan and palm trees. By the end of the project, the church will have a glass and granite front opening straight onto the pavement, with barely a third of the wall remaining.

Menear said: 'It is true that construction has commenced after four years of careful planning and preparation.' He said the two-storey development was necessary to cope with a growing congregation that left the 470-seat church fully packed.

'Although we have confirmed from a range of respected heritage experts that the wall is not of any special heritage value, we accept that it may have some visual and emotional value to some people,' Menear said.

Antiquities board member Tony Lam Chung-wai disagreed that retaining the whole wall was not feasible. 'It's a matter of aesthetics and costs,' he said. 'You can always set it back a bit and protect the wall with retaining structures , although it would be more expensive.'

Less glass could be used in the new design to keep the solidity of the original landscape, Lam, a conservation architect, suggested. According to its website, the church had only raised HK$69 million as of last week - not even half the project's cost.

The church said alternatives to redevelopment had been considered, including using the Tsim Sha Tsui Kai Fong Association Hall next door. But St Andrew's said the decor and facilities were not ideal.

The project would give the church 'high visibility, taking the church to the community and does not need to fulfil expensive planning permission', according to its website.

Ng Cho-nam, one of the members of the antiquities board who had objected to removing the stone wall in two board meetings in 2009 and 2010, said: 'The church totally misses the point if they say the stone wall is not of heritage value because it was not a special design. What makes it special is the landscape and location.

'The case again shows the limitation of the advisory board ... I need to bid farewell to this last bit of old Nathan Road, where century-old trees are collapsing on one side and a landmark wall is falling on the other.'

A Development Bureau spokeswoman said the antiquities board had noted that the final decision would rest with the church despite some members' concerns.

'The Antiquities and Monuments Office prepared a counterproposal and submitted the documents in April last year for the church's consideration, in which the existing rubble wall can be preserved. However, the church has not given any feedback so far,' she said. The present redevelopment plan is the outcome of revisions to proposals put forward between 1994 and 1997, which involved demolishing historic buildings and which the antiquities board did not support.

Under the government's counterproposal, the auditorium's main access would be via an elevated garden and the frontage along Nathan Road would be lost. The gross floor area might also have to be reduced, the bureau said.

$155m

St Andrew's is spending this much, in HK dollars, to build an underground development, including an 850-seat auditorium