A love story with a sci-fi spin, Sir Alan Ayckbourn's 76th play Surprises comes to Watford Palace next week. We chat to the playwright about his new comedy, described as 'a play with its head in the future, but with its heart in the past'.

Your latest play is called Surprises, tell us about it.

I’ve described it as a play with its head in the future, but with its heart in the past. Surprises is essentially several love stories but love stories that have a spin on them. It’s science-fiction but used as an allegory - as most good sci-fi is - to reflect what’s happening today and the issues I’ve picked up on recently.

What issue is Surprises dealing with?

To put it in a nutshell, it’s about what might happen with longevity. I’ve been reading a lot of articles recently about the strain the increasing elderly population is going to put on the National Health Service. The chances of people living longer and longer as the centuries go by are increasingly plausible and certainly quite interesting dramatically. Most of you can already be replaced - although I think the brain will be the last thing it will be possible to replace - but practically everything else is fast becoming a spare part!

How do you think that will affect us?

I have a character in the play who’s 120 years old and says, ‘I’ve just seen my doctor for a check up and he says if I take good care of myself, I probably have another good 60 years.’ He’s already retired twice, had several lifetimes and doesn’t know what to do next. If we’re not able to plan our lives for the long term, we are going to be in that situation, which will pose some interesting problems.

The play also asks what happens to relationships when this longevity happens. Most relationships - never mind marriages - are based on a life expectancy of three score years and ten. So what happens when both of you live to twice that age? Can you sustain that relationship? A lot of people find it hard to sustain a marriage at a normal length of 20, 30 or 40 years. But if we’re going to potentially have relationships going on for 100 years, maybe they will become difficult to sustain. Certainly some people will waiver slightly: ‘I promised this man my life, but do I have to stay with him all that time?’

Beneath this idea of longevity is also an assumption that longevity will be available to anyone - providing they can afford the medical advances.

Oh yes. Surprises is set in the world of the seriously successful. I think the division between rich and poor is likely to grow in the long term; the division of wealth will get increasingly lop-sided. There’s no easy solution as all that happens when you try to prevent that division is that other people just get the wealth - a different class of people. Realistically, once you have a pot of money and you leave several people in a room to split it up, someone will come out with more of it than the rest.

There’s also an element of time-travel in the play, but there is a suggestion that technology doesn’t necessarily offer solutions and is only as infallible as those who use it, which is to say, not at all.

Isn’t that always the case, whatever happens? We say, ‘This is such a wonderful invention!’ and then 20 years later, we think, ‘why the hell did we invent that?’ Our ability to misuse an invention like time-travel is enormous. It’s terribly dangerous as once you try to start altering the past to affect the present, you’re bound to get into all sorts of trouble. Presumably it’s open to all sorts of unscrupulous people from those trying to predict the Grand National winner onwards. So time travel is no solution to problems for my characters and as one of the characters says, ‘it spoils the surprise of life’ and surely life is intended to be a surprise.

It seems to be a recurring theme of your plays that technology never tends to work quite as we expect it to.

I like the idea of the film director Ridley Scott’s worlds where everything is a bit off - things fall off the technology and break. These are worlds which are slightly battered and everything is not human proof. The fact is our machines are affectionately created with the best of intentions, but then we get our hands on them....

Surprises also touches upon the idea of avatars and how - even now with social networking - we use technology to change who we are.

We can pretend to be someone different when we’re behind a computer and never likely to meet the other person, but I actually think that’s just an extension of what we’ve always done in real life. We reach an age where we leave our parents and grow a little independent, then we meet someone we rather want to impress and we’re free to create a personality for them. Unfortunately, we’re not very good at it and it tends to slip away! The fatal thing to do is to take him or her back to meet your parents, who are completely in the know about who you really are! Parents are like some terrible recording machine going, ‘ah-ha here’s a picture of when you were 15 and spotty and not as cool as you now appear to be! Oh and here’s one with your teeth in braces, painfully shy and not at all the elegant 22 year old now standing in the room.’

Surprises is at Watford Palace Theatre from March 5 to 9 at various times. Details: 01923 235455