By Stephen Smith
BBC Newsnight Culture Correspondent
Watch the film
If it wasn't for the impeccable gallantry of its principal passenger and - it has to be said, his mature years - you could easily mistake BB King's tour bus for a passion-wagon.
The door jerks ajar with the report of an air brake, to reveal the titles of his greatest hits worked in electric-blue neon over each stair.
Inside, the thermostat is set at an inhibition-shedding toasty, the better to remind the bluesman of his origins in the cotton fields of the Mississippi delta.
Even the bunk beds of his long-time aides de camp, swagged as they are with creamy drapes, recall the imperishable sleeping-car scenes from Some Like It Hot.
When King - plain "B" to his friends - is finally encountered in his private lair at the rear of the bus, he's at the joystick of his personal entertainment system.
He's enjoying a Blues DVD on a flatscreen. Mahogany-effect panels conceal winking servers that power his state-of-the-art online options.
'Ruled by women'
"Flick that button there," he says, indicating a knob by an armrest. A moment later, I feel the couchette beneath me sliding silkily out from the wall of the bus, impelling me gently into the reclining position. Composing mournful blues which begin Woke Up This Morning, just isn't an option with this baby.
King is hardly an ingénue where the bedroom arts are concerned. He's been married twice, albeit the last union was dissolved so long ago that his resumed bachelorhood has already lasted for decades.
BB King will tour the UK later this year
He has reportedly fathered 15 children by various partners. And by his own account, he is a hopeless enthusiast of the fairer sex.
"They rule the world for guys like me. As I've got older, I've learned to respect them more," he says. "To me, they are more important than we are: how many babies have you had?"
"But you know, because I like women doesn't mean I want to sleep with them all!"
King, it may be worth stating, is 83 years old.
Far from being a diabolical den on wheels, it seems his tour bus is a thrifty alternative to hotel rooms for a musician who still clocks up north of 200 appearances a year.
It's a remarkable tally, especially for a man who doesn't enjoy the rudest of health (he is generously proportioned, and suffers from Type Two diabetes).
The guitarist's only concession to the years is to play his set sitting down, though he acts as though he'll stay on stage until the last fan has had his fill of King's trademark "trilling" licks and corny gags.
Tonight he's nattily attired in a bespoke three-piece suit. It's stagecraft he learnt from his old mentor Frank Sinatra, who helped King to find bookings in Las Vegas when "coloured" acts endured segregation.
King is about to leave the tour bus and go on stage yet again, at a 1,500 seater venue in Philadelphia. Earlier this year, he collected his 15th Grammy award, for his album One Kind Favor.
BB King on US President Barack Obama
It is a long way from playing on the street corners where as a young man King could make more money in an afternoon than he would all week driving a tractor. He was self-taught, and his trademark style began as an attempt to mimic the flights of rhetoric achieved by his pastor in the pulpit on Sundays.
Even though King's illustrious resume includes opening for the Rolling Stones and collaborating with U2, the need to pay the bills, he says, is what keeps him on the road today.
"We used to play so many shows because the radio stations wouldn't play our records. If you can't get your songs to people one way, you have to find another."
King is the undisputed maestro of the blues, hailed by Rolling Stone magazine as one of the three greatest guitarists of all time. But he doesn't seem to recognise this himself, apologising for his "fat hands" and his failure to master chords.
Fear of fading
For all the miles he's clocked up on the road, he's never quite outrun the shadow of his humble origins.
The opening track of his latest album is morbidly entitled, See That My Grave Is Kept Clean. The song was written by Lemon Jefferson, a hero of King's, and the words proved to be grimly prophetic.
"When you don't have much money, you worry that they'll just put you in the ground someplace and your loved ones won't know where you are.
"After Lemon Jefferson died, I went to see where he was laid to rest. Do you know, I couldn't find the spot! This was a great master of the blues and he didn't even have a headstone."
As unlikely as it seems, the fear of an ignominious end in a pauper's grave haunts King, too.
Asked if he fears death, he says: "Well not as much as I used to, but I'm still working on that. You know what I'm saying, to make sure I have what I need at my death. To have a place where people know who I am."
Watch Stephen Smith's film on BB King in full on Newsnight on Thursday, 30 April, 2009 at 10.30pm on BBC Two.