upon to determine the challenge. However, when commenting on a challenge, the arbitrator should exercise caution before deciding whether to respond to criticisms directed at the arbitrator's conduct advanced by the challenging party, or to argue the merits of the challenge (otherwise than by simply declining to resign). The challenged arbitrator must restrain from attacking the party raising the challenge lest that provides the decision maker with independent grounds to uphold the challenge. For example, a recent case in Ecuador highlights the importance of not responding to a challenge as the chair disqualified the arbitrator because his "allegations about the ethics of counsel" for the party bringing the challenge demonstrated an apparent lack of impartiality.(2) Similarly, a division of the London Court of International Arbitration concluded in a 2001 case that while the substantive grounds for the challenge did not give rise to justifiable doubts as to the arbitrator's impartiality or independence, the challenge ought to be upheld considering "the self-evident tension and ill-feeling" resulting from the challenge.(3) In that case, the challenged arbitrator had described the challenging party's submissions as "fictitious, false and malevolent". More recently, the English Commercial Court upheld an application to remove an arbitrator based in part on the arbitrator's aggressive response to a party's enquiries regarding potential conflicts of interests.(4) Comment The lesson from these decisions is that a challenged arbitrator should cooperate with the decision maker by providing observations as to the factual bases for the challenge. However, the challenged arbitrator should be prudent in addressing the merits of the challenge. In no circumstances should the challenged arbitrator appear to descend into the fray or display animosity toward the challenging party. Endnotes (1) Saad Buzwair Automotive Co v Audi Volkswagen Middle East FZE LLC. (2) Burlington Resources inc v Republic of Ecuador (ICSID Case ARB/08/5). (3) LCIA Reference 1303, 22 November 2001. (4) Cofely v Bingham and Knowles 2016 EWHC 240 (Comm).