A wellhead apparatus having an external sealing apparatus for clamping a wearbushing (210, 210a) within a tubing member of larger internal diameter, the apparatus comprising a. a wearbushing (210, 210a) having a first diameter with a sealing zone defined thereon; b. an outer tubing member having an inner circumferential wall with a sealing zone therein, wherein the wearbushing (210, 210a) is positioned substantially concentrically within the outer tubing member having an outer circumferential wall with a sealing zone therein; and c. a compression system mounted outwardly of the outer tubing member adjacent the sealing zones and operable for compressing the outer tubing member into circumferential contact with the wearbushing (210, 210a) for engaging the sealing zones thereof, wherein the sealing zone is a metal sealing surface on said wearbushing (210, 210a) and said outer tubing member for defining a circumferential metal-to-metal seal when the compressions system is activated; and characterised in that: the wellhead apparatus further comprising an inner tubing hanger (212, 212a) which is releasably secured to the wearbushing (210, 210a), and an inner tubing member, the wearbushing (210, 210a) being releasably secured above the inner tubing hanger (212, 212a) and the inner tubing hanger (212, 212a) being secured to the inner tubing member; and the activation of the compression system is arranged to lock down the wearbushing, the inner tubing hanger (212, 212a) and the inner tubing member. a. a wearbushing (210, 210a) having a first diameter with a sealing zone defined thereon; b. an outer tubing member having an inner circumferential wall with a sealing zone therein, wherein the wearbushing (210, 210a) is positioned substantially concentrically within the outer tubing member having an outer circumferential wall with a sealing zone therein; and c. a compression system mounted outwardly of the outer tubing member adjacent the sealing zones and operable for compressing the outer tubing member into circumferential contact with the wearbushing (210, 210a) for engaging the sealing zones thereof, wherein the sealing zone is a metal sealing surface on said wearbushing (210, 210a) and said outer tubing member for defining a circumferential metal-to-metal seal when the compressions system is activated; and characterised in that: the wellhead apparatus further comprising an inner tubing hanger (212, 212a) which is releasably secured to the wearbushing (210, 210a), and an inner tubing member, the wearbushing (210, 210a) being releasably secured above the inner tubing hanger (212, 212a) and the inner tubing hanger (212, 212a) being secured to the inner tubing member; and the activation of the compression system is arranged to lock down the wearbushing, the inner tubing hanger (212, 212a) and the inner tubing member. the wellhead apparatus further comprising an inner tubing hanger (212, 212a) which is releasably secured to the wearbushing (210, 210a), and an inner tubing member, the wearbushing (210, 210a) being releasably secured above the inner tubing hanger (212, 212a) and the inner tubing hanger (212, 212a) being secured to the inner tubing member; and the activation of the compression system is arranged to lock down the wearbushing, the inner tubing hanger (212, 212a) and the inner tubing member.