A number of European countries, among them the UK and Spain, have opened up their Directory Enquiry Services (DQs) market to competition. In Spain, both local and foreign firms challenged the incumbent as of April 2003. The latter raised its rivals' costs and forced quality downgrading by providing an inferior quality version of the (essential) input, namely the subscribers database. We illustrate how it is possible to quantify the effect of the practice in a situation where an entrant has no previous history in the market. We use the UK experience to construct the relevant counterfactual, that is, the but-for scenario. After controlling for relative prices and advertising intensity, we find that one of the foreign entrants achieved a Spanish market share substantially below what it would have obtained in the absence of abuse. While the case was taken to Court and the nature of the abuse was recognized, the amount of damages awarded was limited to evidence of invoice-based inflated input costs, while estimates derived from construction of the but-for scenario were dismissed. This initial ruling was upheld on appeal. At the time of writing, an appeal had been lodged with the Tribunal Supremo (highest Appeal Court) regarding the quantum of damages. We believe that the limited amount of damages probably reflects a mixture of an overly conservative attitude towards damage awards, coupled with a lack of understanding of the underlying economic reasoning of the case, as well as of the quantitative evidence presented by the aggrieved party.