I have no idea whether this is true, but it’s a cute story. From Richard Kay’s Mail Online column:
Plummy-toned Old Etonian actor Damian Lewis didn’t seem to care who could hear as he regaled his wife, actress Helen McCrory, and their children Manon and Gulliver on the top deck of a No.  14 bus travelling down Piccadilly.
‘His theatrical projection drowned out the destination announcements,’ says a fellow passenger. ‘I assumed at first it had to be someone on their mobile. I was six rows away yet I could hear his conversation crystal clearly.’
The Band of Brothers star was recalling bumping into the National Theatre actor Paul Freeman. Says my exasperated traveller: ‘Lewis suddenly declaimed: “He was Claudius to my Hamlet.â€â€™ Fancy…
Thanks to oziegirl17.