In combination with a body defining an annular space and a member received for rotation or linear movement within the annular space, an annular seal includes a first sealing member defining a first sealing portion disposed in constant engagement with a peripheral surface of the member during the rotation or the linear movement thereof, a second sealing member defining a second sealing portion disposed in constant engagement with the first sealing member and radially aligned only with the first sealing portion, and a fluid pressure directed at least onto the second sealing member, whereby the second sealing portion is configured to bias the first sealing portion into the constant engagement with the peripheral surface of the member.