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 :Mark Nicholls in the Oxford Dictionary of National Biography (2004) agrees with you. In his article on Catesby he says  
 :Nicholls cites this to ""TNA: PRO SP 14/216/136"", although he doesn't explain exactly what that source is. I can't trace it online, except that Nicholls uses it again in his 'Strategy and Motivation in the Gunpowder Plot', in The Historical Journal 50 (2007), 787–807.   "