The doctrine of 'prosecution history estoppel' (PH estoppel) as developed in the United States has strong intuitive appeal, especially when applied to counterbalance a related patent law principle, the doctrine of equivalents. The doctrines are receiving increasing attention in US patent decisions, to the point where one patent litigator recently compared them to "two cars that keep bumping fenders. They are frequently returned to the shop for repairs". Could PH estoppel find its way into UK patent law? This article briefly examines the doctrine, its evolution in the US and the problems associated with importing the doctrine into the UK. As the EU legislation stands, Article 69 and the Protocol to the European Patent Convention (EPC) pose serious obstacles to using the doctrine directly in claim construction. However there appears to be some scope to apply the doctrine as a limited form of defence in infringement actions.