names that can hardly be imagined apart. Marriner, originally a violinist, founded the academy as an ensemble of friends who met in his London living room and played together without a conductor. They made their public debut in 1958 at the church in Trafalgar Square that gave them their name; Marriner directed from the leader's chair and every hand-picked member of the small band responded with the vibrancy and alertness of chamber musicians.
This year Marriner will be 90 - there are birthday concerts planned in London and Germany in the spring - and for the past two seasons the Academy has been under the musical directorship of another, much younger musician for the first time. That is no easy mantel to take on, but for violinist Joshua Bell there is no question of trying to replace the orchestra's illustrious founder.
"I really don't think of it as taking over his mantel," Bell says. "My association with the orchestra goes back about 27 years - that's when I made my first recording with them under Marriner - and over the past decade I have performed with them a lot and they have come to feel like family."
The 46-year-old American made his concerto debut with the Philadelphia Orchestra when he was 14 and has been a fixture in the international spotlight ever since. Somehow he has always been a more rounded, more grounded kind of touring virtuoso than many, though. Affable and athletic, ever boyish in his handsome looks and ever down-to-earth in conversation, he makes sure to squeeze in chamber music and Sesame Street gigs among his star tour dates around the globe.
There was his 2007 stunt in the Washington DC subway, when he donned a baseball cap and busked for 45 minutes to see how many commuters would stop to give him the time of day (seven). And with a towering discography now approaching 50, Bell's latest release was an easy-listening Christmas album with guests that included Chick Corea and Bradford Marsalis.
Yet for all that, Bell considers his work with the Academy as the very pinnacle of his career to date. He upholds Marriner's founding tradition of directing the orchestra from the leader's chair - something that caused some teething problems in getting the right balance between airtight ensemble and Bell's trademark flamboyant stage style (he tends to move around a lot). But the partnership has increasingly drawn exciting results. "For me, it's the greatest huge thrill," Bell says. "I get to do it all: play my concerto and direct it, then lead a great symphony that I would usually be sitting in the audience listening to in the second half of a concert."
For somebody who has spent decades flying into one rehearsal concert dates around the world, the level of detail and scope for development that this musical directorship allows him is a rare treat. The only experience that matches it, he says, is playing chamber music with regular collaborators such as cellist Steven Isserlis.
"Sure, I have been learning on the job. The players are becoming more attuned to my body language and I am becoming more attuned to what I should and should not do to communicate effectively with them. Everyone is on the edge of their seats; everyone has to lead. There is a feeling of empowerment about that which can be extremely positive."
"It also helps that the musicians like each other," he adds with a laugh. "On tour they are always out together eating and drinking together after concerts. That can't be said about all orchestras!"
Beethoven's early symphonies have formed the backbone of Bell's programmes with the Academy thus far (they perform the first in Edinburgh on Monday). He acknowledges that when it comes to large-scale symphonic repertoire it can't always be a simple case of musicians listening alertly; there are corners of the Eroica or the Fifth that need firm direction to stick together. So over the past couple of years Bell has devised a sort of hybrid leader-conductor role, whereby he sits on a slightly higher chair so that he can be seen by the orchestra, and shares leading responsibilities with his desk partner so he can duck out of playing and straightforwardly conduct in dangerous patches.
With this set-up, he says, there is not much repertoire he would be afraid to touch. "When I first thought of doing the Eroica it seemed mad; today we have done it for the past four nights on the trot and it is incredible each time. I am beginning to think there is nothing that can't be done this way. I'm excited about trying the Brahms symphonies soon." And beyond that? "You mean like The Rite Of Spring? Why not?! The big secret is orchestras don't absolutely need a conductor to play well together."
Joshua Bell and the Academy Of St Martin In The Fields are at the Usher Hall, Edinburgh, on Monday.