During the recent repair of the Entrance Portal, the City of London’s crest required particular attention and careful collaboration between conservators, stonemasons and carvers. The resulting schedule of repairs drew from a wide range of conservation methods and materials.

The City of London Crest, carved in Caen stone, is located centrally above the main arch of the portal. It consists of a shield framed by a medallion with a Muscovy hat on top, two dragons as supporters and the City of London’s motto beneath that reads ‘DOMINE DIRIGE NOS (O LORD, DIRECT US)’. The crest is contained within a gothic architectural framework. This includes three canopied niches, decorated with ribs, crockets and finials, and supported by a base of foliate corbel tables.

The Crest had suffered severe decay due to environmental processes of degradation and the use of countless unsympathetic repair materials. Sadly, hard impermeable cement repairs had caused an accelerated rate of decay, undermining the aesthetic, legibility and structural stability of the carvings. As a result of these early poor interventions, the original Caen stone was heavily saturated, friable and fractured throughout.

The condition of the stonework and variety of repair materials called for a holistic method of repair. The stone was carefully defrassed and all biological growth removed. Following site trials CaLoSil E5 and E25 nanolime were used to consolidate the exposed stone surfaces. The CaLoSil was applied using a brush and small syringe, which allowed for a more accurate and targeted treatment. The area was covered between applications to prevent premature evaporation of the ethanol and aid deeper penetration. The treated area was lightly sprayed with water throughout the process to maintain appropriate conditions.

Any surrounding stonework that was beyond salvage, such as the shield, medallion, Muscovy hat and motto were recarved in Caen Firm B Bed. The stone is a ‘ferme’ variety of Caen, sourced directly from France to offer a sympathetic match for the original and offering superior weathering characteristics. Continuing London Stone Conservation’s close association with the City and Guilds of London Art School the foliate corbel tables were recarved by students from the college’s Historic Carving department.

Previous cemetitious mortar repairs were replaced in a porous and permeable lime putty mix. Repeated ornament, such as the crockets and finials to the canopied niches, were reinstated with cast replicas. Silicone rubber moulds were made of the undamaged originals and then cast in a prompt natural Roman cement and aggregate mix. Finally, the crest was coated with a colour matched casein-bound limewash to unify the appearance and provide a further protective surface.