If there is one thing I have learnt on this job, it's that you can never second guess how an interview is going to turn out.

When I phone Lulu ahead of her Summer Swing concert at Kew Gardens this Thursday, I have my questions all mapped out. How did it feel being passed over for the X-Factor job in favour of Cheryl Cole? Are you and your manager Louis Walsh still talking? Do you actually shop at Morrisons?

In the event, we end up talking about the American presidential election instead.

That's not to say there isn't some luvvie action first. "What do we need so many phones for?" asks the singer, picking up my call while still on another line. "Can you hold on a sec..."

This is interview number three of the day for Lulu, who has already filmed segments for The Sunday Night Project and Gok's Fashion Fix. Gok, she says, is "fabulous, a sweetheart, absolutely adorable". He is even bringing his parents to see her perform at Kew.

At last year's Summer Swing, she was merely a guest performer at Jools Holland's gig. This time, it's Lulu's turn to take centre stage, supported by friends Kiki Dee and Paul Carrick. Not a bad life, eh?

"Are you kidding?" she says in that familiar Scottish-American burr. "It is hard to keep in touch when everyone's busy doing their own things, so it's an absolute joy when you do hook up. Kew's a pretty magical place and when you have this same wonderful thing in common - music - it's like there has been no real gap, like time doesn't exist."

How long have Lulu and Kiki been friends? "We've known each other since the 60s," she says. "All of us singers used to meet each other at gigs, you know." She pauses. "Or maybe we know each other through Elton? I can't remember."

No wonder details get a bit blurry after four decades in the business. Hard to believe but Lulu's biggest hit, Shout, was released in 1964, 30 years before her comeback with Take That single Relight My Fire.

The pint-sized popstar turns 60 this November. But not only does she not seem to age, she actually looks younger with each birthday (and Botox).

"It's like John Miles says: music is my first love and it will be my last," says the self-confessed treatment addict. "But, in order to be equipped, I like to exercise my voice and my body and my mind."

Currently studying for a social sciences degree with the Open University, Lulu spends as much time reading as she does down the gym.

"You never stop learning," she marvels. "There's this great writer in the New York Times - Thomas Friedman. I have been reading the way he left school and went off to report in Beirut. As a Jewish American! You hear about people doing things like this and you think, my God, it is incredible!"

On a roll now, she continues. "Look at Barack Obama. It looks like he's going to be the first black president. So the world is full of so many fascinating things. You can't take it all in but to be interested - that's what keeps you vital."

Lulu and Friends, Summer Swing Concert, Kew's Royal Botanical Gardens, July 10, 6.30pm for 7.30pm, £35, 0871 231 0834, visit kew.org/summerswing or seetickets.com