In the UK, about 1 in 600-700 babies is born with a cleft of the lip and/or palate. A proportion of children with this condition develop a concave facial profile whereby the lower jaw appears protruded. Maxillary advancement surgery, which is usually undertaken in late adolescence, aims to realign the upper and lower jaws by advancing the former. Although this can improve the adolescent’s facial profile, this surgery can however lead to deterioration in speech, whereby too much air flows through the nose during talking, reducing intelligibility. There is currently no consensus on this and no defined way to predict which patients will be at risk of this before surgery. This study will employ a range of speech evaluation techniques to explore this objectively with long-term follow-up. The study will enable us to provide future patients who seek this surgery with more accurate and objective information regarding the potential risks on speech.