In April 1578, the Spanish ambassador, Bernardino de Mendoza, had written to King Philip II of Spain that it had been proposed that if Anjou were to travel to England to negotiate his marriage to the Queen, Oxford, Surrey, and Windsor should be hostages for his safe return. Anjou himself did not arrive in England until the end of August, but his ambassadors were already in England. Oxford was sympathetic to the proposed marriage; Leicester and his nephew Philip Sidney were adamantly opposed to it. This antagonism may have triggered the famous quarrel between Oxford and Sidney on the tennis court at Whitehall. It is not entirely clear who was playing on the court when the fight erupted; what is undisputed is that Oxford called Sidney a 'puppy', while Sidney responded that "all the world knows puppies are gotten by dogs, and children by men". The French ambassadors, whose private galleries overlooked the tennis court, were witness to the display. Whether it was Sidney who next challenged Oxford to a duel or the other way around, the matter was not taken further, and the Queen personally took Sidney to task for not recognizing the difference between his status and Oxford's. Christopher Hatton and Sidney's friend Hubert Languet also tried to dissuade Sidney from pursuing the matter, and it was eventually dropped. The specific cause is not known, but in January 1580 Oxford wrote and challenged Sidney; by the end of the month Oxford was confined by the Queen to his chambers, and was not released until early February.