We hear that you're getting replacement knees for Christmas. What happened to the old ones?
Halfway through a recent trip to Africa, my knees suddenly collapsed. We were in Masai country and, as you probably know, a Masai warrior is given a stick once he has killed a lion single-handedly in combat. I didn't kill a lion but I got a stick. They're better than you'd get on the NHS! So I'm getting them fixed. I wish the doctors would operate on them both but they won't, so I'm having them done one at a time.
So does that mean you'll have to put your feet up this Christmas?
I've been away a lot this year and I've made a lot of films, but even when I'm home, I have things to do most days and I don't mind doing them. I like writing a script, or catching up on correspondence. It's not that I'm putting on a turn of speed because I can see the wheelchair around the corner. It has just happened that way.
Don't you ever stop working? After all, you're 86 now...
I can tell you exactly how many days I'll have worked this year. And that's 365. Christmas Day is my only time off.
So how will you spend your one day off this year? With the family?
I expect there will be about 14 of us, including my son Robert and daughter Susan. There'll be at least one grandchild - the other might be chased off somewhere else by her boyfriend. It's always nice to see my grandchildren because I don't know them all that much because they were born and brought up in Australia.
Is it better to give than receive?
I don't like to receive many presents. When you're my age, you're getting rid of stuff, not accumulating. When the kids were younger, it was a big thing. It's not such a big deal now. I do like to give gifts, though. That's something special, to give intimate things. I can't reveal what they are, as that will give the game away before the family know what they're getting!
Once Christmas lunch is cleared away, do the Attenboroughs like to play games - charades maybe?
Certainly not! No, I'm not a big game player. There are a lot of things to do before you have to resort to inventing things.
What about 2013 - will you be slowing down, or speeding up?
I hope to go to China to film a new 3D series. Travelling can be hellish, but when you are asked to go to one of the greatest places in the world, what are you going to do? There are no free rides in this world. When you get there, you meet old friends or new guys who are talented and great company, and that's half the fun of it. It's no great effort on my part to endure a few hours of discomfort to see the things I get to see. That's no hardship at all.
David Attenborough presents Africa on Wednesday 2 January on BBC1, and Galapagos 3D on New Year's Day on Sky1 and Sky 3D (Sky 217).