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P7144GB2 - 1 - 165105/02 CONNECTORS This disclosure relates to connectors suitable for connecting a subsea wellhead system and a second component. 5 Connectors for use in connection with subsea wellheads are typically used to connect the subsea wellhead (typically the high pressure wellhead housing) and an element of subsea riser system equipment, for example, but without limitation, a blowout preventer (BOP) - which may comprise a lower stack and a lower marine 10 riser package (LMRP), a Christmas tree (which may also be referred to as a subsea tree), an other element of well control apparatus, or a riser string. According to a first aspect of the present disclosure, there is provided a connector for connecting a subsea wellhead system to a second component, in which the 15 connector comprises a locking element configured to engage with a locking portion of the wellhead system and a locking portion of the second component, a gripping element configured to engage with a gripping portion of the wellhead system, and 20 a compression element, in which the gripping element and the locking element of the connector are spaced from each other, and the compression element is configured to introduce compression into the wellhead system between at least the locking portion and the gripping portion of the first 25 component. It is to be understood that the compression introduced into the wellhead system by the compression element is additional to any compression that is introduced into the wellhead system when the second component is connected to the wellhead 30 system by the connector. In greater detail, it is known that wellhead systems are normally configured to extend in a vertically upwards direction, and the second component is connected to the vertically uppermost end of the wellhead system. As a result, typically the weight of the second component is exerted on the wellhead system in a vertically downward direction. The compression introduced into the P7144GB2 - 2 - 165105/02 wellhead system by the connector of the present disclosure is additional to any compression introduced by the second component. It has been found that subsea wellheads that have been subsea and in use for a 5 period of time before it is desired to connect or reconnect an element of subsea riser system equipment (such as a subsea tree, a tree system spool, a blowout preventer (BOP), a riser string, a kill spool, a tubing hanger spool, a capping stack, an in place capping stack, a kinetic blowout stopper (KBOS) standalone, a high pressure cap, a workover stack, or other element of well control apparatus) may 10 have been exposed to or suffered from damage caused by the previous use. For example, the previous use may have included previous drilling activities and subsequent oil extraction. Such damage may include, for example, one or more fatigue induced cracks in the wellhead. Such cracks may be the result of cyclic loading. They may reduce the effective wall thickness of the wellhead and as a 15 result lessen the strength of the wellhead and increase the risk of mechanical failure of the wellhead. In a subsea environment it is not easy to identify fatigue induced cracks in the wellhead and, as a safety precaution it may be necessary to assume that such 20 cracks are present. The assumed increased risk of failure of the wellhead may be sufficiently high that connection of an element of subsea riser system equipment to the wellhead, and the performance of subsequent operations through the wellhead, is not possible within the safety limits that govern the activities of drilling rig operators. 25 Another cause of damage to a subsea wellhead may be high load events, for example accidental impact loads from dropped objects that have hit or landed on the wellhead. Such high impact loads may be the result of direct contact of a source of the high load with the wellhead. 30 High load events may damage the wellhead as a result of transmission of loads into the wellhead from an element of subsea riser system equipment via the connector that connects that equipment to the wellhead. The high load may be applied to the equipment as a result of accidental impact on the equipment, position loss of riser 35 connected vessel, loss of riser tension which is likely to result in subsequent large P7144GB2 - 3 - 165105/02 bending loads, loss of wave motion compensation, and subsequent accidental tension loads. Post event investigations may conclude that the original strength of the wellhead, or 5 parts of the wellhead such as the uppermost part, must be assumed to be reduced as a result of the accidental impact loads, high load event, or fatigue induced loading. An advantage of the connector of the present disclosure is that the connector may 10 be used in connection with subsea wellheads that may have been exposed to or suffer from such damage as is described above. This is because the introduction of compression into the wellhead by the compression element has the effect of closing any cracks and applying a level of compression to any cracks and the remaining material, and as a result strengthening the wellhead. This may render the wellhead 15 safe for the connection to an element of subsea riser system equipment and make the desired well activity that necessitates the connection of the connector possible. Furthermore, the connector of the present disclosure may avoid the need to replace the wellhead. In the event of a severely damaged wellhead the use of a connector of the present disclosure may have the advantage that it can enable the well 20 activities necessary to established safe closure of the well such that the damaged wellhead may be removed. A further advantage of the connector of the present disclosure is that if it is used on a undamaged wellhead system the part of the wellhead system that is put in 25 compression will be more protected from damage such as that described above than a wellhead system to which a conventional connector is connected. In an embodiment of the above embodiment, the connector is a valve assembly connector. 30 In an embodiment of the above embodiment, the wellhead system comprises one or both of a high pressure casing and a high pressure housing. The one or both of the high pressure casing and a high pressure housing are referred to herein as “the wellhead”. 35 P7144GB2 - 4 - 165105/02 In an alternative embodiment of the above embodiment, the wellhead system comprises a combination of (i) one or both of a high pressure casing and a high pressure housing (the one or both of the high pressure casing and a high pressure housing are referred to herein as “the wellhead”) and (ii) one or both of a low 5 pressure casing and a low pressure housing (the one or both of the low pressure casing and a low pressure housing are referred to herein as “the conductor”. In an embodiment of any of the above embodiments, the wellhead is longitudinally extending with a central axis and an upper end. The upper end of the wellhead has 10 an end face. The end face of the wellhead typically faces toward the surface of the sea. In this context, the upper end is the end that is vertically uppermost when the wellhead is positioned for use and at least partially extending out of the seabed. In an embodiment of any of the above embodiments, the locking element is 15 configured to engage with a helical thread, a flange, or other known arrangement suitable for connecting t...