Please suggest a new anti-spammer question for HoL sign-up

About six months ago it seemed like we were getting more and more spammers leaving annoying messages on people's member pages. With the thought in mind that this must be very annoying for members and that ultimately if people keep getting spammed they'll quit the site, I decided to add yet another barrier to the sign-up process. This time I added a question. Since it seems that the spammers were coming from the US and Africa, I went for something that I thought most people who live here would know or could easily find out, but that wouldn't be known by people who live abroad. I've also offered the opportunity for people who want to sign-up but don't know the answer to email us and ask for the answer.

The question is:

Name the most famous sci-fi 'doctor' on British TV

Since that question went up we've had no spammers at all, but are still getting 30 - 40 sign-ups each week. I'm sure that some people are excluded, but I've figured that 's a price worth paying for the health of the site.

Yesterday an email from a site member pointed out that non-English Harringaeites may not know the answer. I'm quiet happy to change it. Any suggestions? The criteria the question needs to meet:

1. Answer likley to be know to those who live in the UK, but less likely to be known to the spammer brigade who tend to live overseas.
2. Not so local that it keeps non-Harringaeites out (for example the person who sent me the mail yesterday pointed out that she found HoL a very useful resource looking at the area before she moved here).
3. A short and simple answer, preferably one or at most two words with the minimum number of variants.