He was concerned 'lest' anyone think that he was guilty. = ('chiefly Brit') He was concerned 'lest' [='in case'] anyone should think he was guilty. [=he was concerned that people would think he was guilty; he did not want anyone to think he was guilty]
She's a talented singer and, 'lest we forget', a fine musician as well. [=we should not forget that she is also a fine musician]
And 'lest' you think I'm joking, let me assure you that everything I've said is true.
(..) we do not ride " " I'll tan your fucking hide " " Ride! " " Kyle's fingers be silver " " Jack's voice then be gold " " But lest you think we're vain " " We know you're all robots and we don't care " " Tenacious D " " We reign! " " We reign " (..)2006 Tenacious D in the Pick of Destiny