Cars in several motor sports series, such as Formula 1, make use of multi-element front wings to provide downforce. These wings also provide onset flows to other surfaces that generate downforce. These elements are highly loaded to maximise their performance and are generally operating close to stall. Rubber debris, often known as marbles, created from the high slip experienced by the soft compound tyres can become lodged in the multiple elements of a front wing. This will lead to a reduction in the effectiveness of the wing over the course of a race. This work will study the effect of such debris, both experimentally and numerically, on an inverted double element wing in ground effect at representative Reynolds numbers. The wing was mounted at two different ride heights above a fixed false-floor in the Loughborough University wind tunnel and the effect of debris blockage modelled by closing sections of the gap between elements with tape. The reduction in downforce compared to the clean wing was measured and the sensitivity to the size and position of the blockage studied. It was found that debris near the centre of the element has a greater impact. CFD simulations were also carried out that were able to correctly predict the trend of downforce with blockage position. The CFD was also used to computationally remove the effects of the tunnel. This confirmed the result seen in experiment that the blockage has more effect on a more highly loaded wing.