Tesco has submitted plans to raise the roof of its Station Road, Harrow, supermarket to squeeze in a mezzanine level that would double the floorspace.
This appears to conflict with earlier indications from the retail giant that it would be able to accommodate the extra floor within the existing roofspace and would therefore not need to alter the exterior appearance of the store at all.
Tesco's application, which has been formally lodged with Harrow Council and will go before the authority's strategic planning company for approval, reveals that three independent retail units will also be built.
The third part of the scheme involves turning the car park into a triple-decked multi-storey, increasing its capacity from 386 to 620 cars. There would be moving walkways linking the car park to each floor.
A range of non-grocery products such as clothes, homeware, white goods and electrical appliances would be housed on the new mezzanine floor while food would be found on a re-jigged ground floor.
James Wiggam, Tesco's corporate affairs manager, previously informed the Observer the expanded store would create 200 extra jobs and that modern construction techniques would mean three-quarters of the supermarket could remain open during building.
He said the extension - which could be open in time for Christmas - generated a favourable reaction from 90 per cent of shoppers who responded to an in-store consultation about the plans.
The store, built on the site of Wealdstone FC's Lower Mead football ground, was opened in 1992 and is one of the busiest in London.