10.3 Long-felt need; commercial success 

Where the invention solves a technical problem which workers in the art have been attempting to solve for a long time, or otherwise fulfils a long-felt need, this can be regarded as an indication of inventive step.

Commercial success alone cannot be regarded as indicative of inventive step, but evidence of immediate commercial success together with evidence of a long-felt want is relevant if the examiner is satisfied that the success is attributable to the invention's technical features and not a result of other factors (e.g. selling techniques or advertising).