Plans to install a new electricity sub-station at 55 Marylebone High Street are facing objections from the Marylebone Association and local residents, primarily due to concerns about potential noise and disruption. The application was discussed at a meeting of Westminster Council's Planning Sub-Committee (1) on Tuesday, 11 November 2025.

Residents are concerned about the impact of the sub-station's noise on their properties. An initial background noise assessment was carried out from a secure location at 2nd floor level to the rear of 55 Marylebone High Street overlooking Devonshire Place Mews. Following concerns raised about how representative this location was in relation to the nearest noise sensitive receptors, an attended noise survey from carried out at ground floor level in Devonshire Place Mews. The closest noise sensitive receiver to the proposed plant has been identified as being the mews house directly opposite at a distance of 9m from the plant. The adjacent building to the south (being the rear elevation of 27 Beaumont Street) is closer at 5m but is screened by the building fabric.

The proposal involves installing louvred double doors and a grille in existing door and window openings on the rear of the building, which fronts Devonshire Place Mews. These alterations are necessary to provide ventilation for the new sub-station.

The Marylebone Association raised concerns about potential noise and highways disruption. Councillor Scarborough supported the objections of residents and requested that the application be determined at Planning Committee.

Residents objecting to the plan cited several concerns, including:

  • The background noise assessment being carried out in an inaccurate location, potentially impacted by noisy building works.
  • The proposal being detrimental to the appearance of the building and the Harley Street Conservation Area.
  • Traffic issues caused by the relocation of a parking bay (though this was later resolved by relocating the substation).
  • Questions about the necessity of a new electricity sub-station at the property.

Despite the objections, Environmental Health raised no objection subject to conditions. The Highways Planning team also had no objections, subject to conditions. Environmental Health imposed standard noise and vibration conditions and a condition requiring the installation and retention of the louvred doors / window with their specified acoustic mitigation performance.

An acoustic report submitted with the application predicted that the sub-station is likely to produce a maximum pressure level of 24 dB(A) at the windows to the properties in Devonshire Place Mews. Environmental Sciences stated that, even with a reduced distance, the sub-station plant is likely to comply with the design level criterion. They noted that an open window still affords a further 10-15 dB loss, so the internal level would be in the region of 15 dB, which is considered to be below the threshold of hearing.

Environmental Sciences recommended conditions controlling noise emission levels and standard noise and vibration conditions. The specific conditions are outlined in the draft decision letter:

  • Condition 6 details the requirements for noise emitted from the plant and machinery, including specific dB levels and measurement methodologies.
  • Condition 7 specifies the vibration limits that must not be exceeded.

Environmental Sciences has reviewed all the documentation submitted and the detailed objections received and confirm they have no objection subject to the imposition of standard noise and vibration conditions and a condition requiring the installation and retention of the louvred doors / window with their specified acoustic mitigation performance.

The draft decision letter includes the following informative: Conditions 3, 4 and 5 control noise from the approved machinery. It is very important that you meet the conditions and we may take legal action if you do not. You should make sure that the machinery is properly maintained and serviced regularly.

With the inclusion of these conditions, the planning application was recommended for conditional approval.