We've had Speaker Martin's for longer than I've been at TWE, but I don't think we've ever had a signed one. I do have an amusing tale about a visiting VIP who wanted a bottle of House of Lords whisky signed by a certain disgraced Tory peer whose books he greatly admired, but I probably shouldn't share that here.
Coincidentally, when I first rocked up to London in 2000 I was working as assistant manager at the Oddbins on Victoria St (it's a Phones 4U these days, nothing to do with me, honest).
My manager at the time was a troubled character (that's putting it politely), but had managed to secure the HOC account for own-label champagne and HOC whisky. The champagne was relabelled Heidsieck Monopole, the whisky was relabelled James Martin 8yo and the volume was phenomenal. We were sending about a pallet of the champagne and 150 bottles of the whisky over every Monday morning, smashing our weekly targets (which had been set before we got the account) with our first sale of the week - which was a lifesaver, as assistant managers in those days (and probably now I shouldn't wonder) had a salary of about 9k, didn't get paid for overtime and had to live off their monthly bonus. So Thank You HOC, without whom I probably wouldn't have been able to get through my first 6 months in London.