a 2006 review of a later Churchill work, The Independent's Paul Taylor described the play as one of the best dramas of the new millennium, and as "superbly compressed and economic". After watching a performance featuring John and Lex Shrapnel, Lyn Gardner of The Guardian dubbed the play "[p]unchy, compact and endlessly inquisitive," arguing that it "is no simple warning against the perils of science messing with nature, but a complex and humane study of parental guilt, regret and responsibility and what it really means to be a father or son." Conversely, Jane Shillings of The Telegraph argued, "The highly wrought writing veers at times towards the mannered, leaving a faint sense that the style of Churchill’s play exceeds its substance, and the issue of cloning has lost its urgency". Don Aucoin of The Boston Globe praised the way the playwright "devotes no time to preamble or writerly throat-clearing, but plunges us straightaway into the play’s central dilemma". In the Chicago Tribune, Chris Jones described A Number as "masterfully written". After seeing a 2020 Bridge Theatre performance, Nick Curtis of Evening Standard argued, "If the background logistics are sketchy – who made the human copies, and why? – the relationships between Salter and his offspring, and their differing reactions to finding that they are not unique, are right on the money. [...] It’s almost exactly an hour long and the ending is abrupt, but Churchill packs more ideas and feeling into that time than most dramatists manage at twice the length." Clive Davis of The Times, however, panned the play as "both too short and too long" after seeing the same performance. Matt Wolf lauded A Number as a "beautiful play", and wrote that it "works not least as a thriller or bit of forensic detection, as Churchill plants clues prompting a reevaluation of the narrative at every turn." Arjun Neil Alim of The Independent stated that "Churchill, a political playwright par excellence, tactfully references current events. [...] Are 'Who are you?' and 'What are you made from?' the same question? Churchill’s answer comes in the form of a character who defines himself by his deeds and his loved ones, rather than the circumstances of his birth." Andrzej Lukowski of Time Out called the play a "masterpiece". Steve Dinneen argued in City A.M. that the work "is remarkable in the way it so gracefully touches upon the great philosophical questions