A public inquiry into controversial plans to redevelop part of one of London's oldest markets has begun.
Butchers say the development will enhance the area
English Heritage claims demolishing the derelict General Market Building would seriously damage a conservation area and wants it repaired and reused.
But developers say rail tunnels in need of upgrading under the site make renovation work unrealistic.
Butchers are backing the development of an office block claiming it will uplift the area and protect their future.
Traders staged a protest outside the General Market Building on Tuesday over claims English Heritage plans would involve relocating the working market.
Greg Lawrence, chairman of Smithfield Market Tenants Association, said: "The General Market Building, not part of today's thriving meat market, is a derelict eyesore in our opinion and Thornfield's proposals will make a real contribution to Smithfield."
But English Heritage said: "English Heritage has no remit on the future of the meat trade."
The public inquiry was ordered when English Heritage opposed plans by Thornfield Properties plc to build a seven-storey office block on the site.
English Heritage said there was "clear evidence" that the building could be repaired and reused in a way that would benefit the entire site.
It also said the proposed replacement was "intrusive" and would "undermine the diversity and human scale of the Smithfield Conservation Area".
But Thornfield Properties said: "What you can't see on the surface is that the Thameslink rail tunnels form part of the building and these tunnels are in need of repair.
"It is the liability of the building owner to undertake these multi-million pound repairs and it can't realistically be done technically or financially without demolishing the building."
Meat has been traded at Smithfield in Farringdon for more than 800 years.
Traders continue to operate out of the Grade II listed West and East markets, built in the 1860s, but other parts, including the General Market added in 1883, have not been listed.
The City of London Corporation said all listed buildings would be protected and that most of the structures concerned were structurally unsafe.