Objections by SE1 residents to the routing of the Thameslink 200 scheme through Borough Market are due to be heard at the public inquiry.
The Inspector Mr Ken Barton is conducting the Inquiry at the LSE's Bankside House where he is due to hear evidence from from Cathedral Area Residents Association and the Bankside Residents Forum from Wednesday 19 October.
The two groups are presenting objections to the upgrade of Thameslink 2000 through the Borough High Street Conservation area and instead proposing what they describe as "a 21st century solution" taking into account changed circumstances since last Inquiry in 2000.
The community groups' new proposal involves re-routing Thameslink trains through the Elephant & Castle which is now the subject of a major redevelopment.
CARA and BRF, backed by Save Britain's Heritage, are objecting to loss of twenty listed and unlisted buildings in the Borough Market area to make way for a concrete and steel viaduct through the Borough Market area.
They are also due to express concern regarding the viability of the market during construction and whether contamination of food from demolitions and a long-term building site may cause closure.
The objectiors have the support of both Financial Times chairman Sir David Bell and Tate Director Sir Nick Serota. Simon Hughes MP is expected to give evidence for the objectors on Thursday morning.