NEC3 ECS: Is an Architect responsible if a sub-contractors design is incorrect and not spotted in advance

Under a D&B contract where the Architect is Novated to the contractor. If the Architect is asked to comment on a Sub Contractors design and forgets to do so, resulting in the Contractor proceeding without having received any comment / approval does the Architect bare any liability if the Sub Contractors design is wrong / not in accordance with the Architects drawings?

In simple terms no, but you need to look at the contract between yourself and the Contractor. The NEC3 contracts do not on the whole have deemed acceptances (the only exception to that being non-response within the compensation event quotation process). In the ECC contract, design acceptance is a hold point, and if the Project Manager does not respond to a Contractors design within the “acceptance period” then the Contractor does not proceed assuming acceptance. They stop, and any resultant delay would be a compensation event.

Here the Contractor should have taken it upon themselves to get your feedback as to their design. Not great that in your example the architect has “forgotten to respond”, but no that would not mean contractually that the Contractor is entitled to assume deemed acceptance, and any liability would now be with the Employer. The Contractor is responsible under 20.1 to “provide the works in accordance with the Works Information”. If their design does not meet that Works Information that would still be their liability (14.1).

Seems to me that both Parties here need to be working closer to ensure issues like this do not occur.