The speed limit for holding is typically 265 kts or Mach 0.83. The bank is limited to turn rate of 3 degrees/sec or a bank angle of 25 degrees, whichever is less. So no matter what speed you were flying, you'd never be pulling more than 1.1G.
But just for the sake of fun... I calculated the Concorde (any airplane for that matter) would be pulling 3.32G if it was in a steady, level 3 degree/sec turn at a speed of 1150 KTAS (~Mach 2). The angle of bank required is 72.45 degrees.