A telescopic assembly comprises a first portion and a second portion and a support bearing assembly that acts between the two portions; the two portions being able to move relatively along a common path during telescopic adjustment; the support bearing assembly being located between the two portions and locating the two portions relative to one another to remove free play between the two portions that would otherwise occur in at least one direction orthogonal to the telescopic movement; characterised in that the support bearing assembly is fixed in position between the two portions by a release mechanism that is arranged, in use, to cause the support bearing assembly to grip both the first and second portions when they are not moving telescopically, to automatically release that grip upon relative telescopic movement of the two portions that exceeds a predetermined distance, and to automatically re-engage that grip when the relative telescopic movement has subsequently stopped.