An aircraft structural assembly comprising: a fuselage portion partially defining a pressure vessel containing a passenger cabin including a cabin floor; and a wing unit attached to the fuselage portion, the wing unit comprising: a first wing extending in a first lateral direction relative to the fuselage portion and a second wing extending in an opposite second lateral direction relative to the fuselage portion; a first pressure fence attached to the first wing, the first pressure fence defining a first part of the pressure vessel partially defined by the fuselage portion, the first pressure fence being attached to the fuselage portion at a first joining location that is disposed vertically above the cabin floor; and a second pressure fence attached to the second wing, the second pressure fence defining a second part of the pressure vessel partially defined by the fuselage portion, the second pressure fence being attached to the fuselage portion at a second joining location that is disposed vertically above the cabin floor, wherein the first pressure fence comprises a first fence skin and the second pressure fence comprises a second fence skin; the first fence skin extends upwardly relative to an upper wing skin of the first wing and also in the first lateral direction; and the second fence skin extends upwardly relative to the upper wing skin of the second wing and also in the second lateral direction, wherein an upper portion of the first fence skin is attached to a first stringer of the fuselage portion and an upper portion of the second fence skin is attached to a second stringer of the fuselage portion; and the first and second stringers are disposed vertically above the cabin floor of the fuselage portion; and characterised in that the first pressure fence comprises one or more first fence frames and the second pressure fence comprises one or more second fence frames; the one or more first fence frames and the one or more second fence frames are attached to respective fuselage frames; and the one or more first fence frames and the one or more second fence frames extend vertically above the cabin floor of the fuselage portion. a fuselage portion partially defining a pressure vessel containing a passenger cabin including a cabin floor; and a wing unit attached to the fuselage portion, the wing unit comprising: a first wing extending in a first lateral direction relative to the fuselage portion and a second wing extending in an opposite second lateral direction relative to the fuselage portion; a first pressure fence attached to the first wing, the first pressure fence defining a first part of the pressure vessel partially defined by the fuselage portion, the first pressure fence being attached to the fuselage portion at a first joining location that is disposed vertically above the cabin floor; and a second pressure fence attached to the second wing, the second pressure fence defining a second part of the pressure vessel partially defined by the fuselage portion, the second pressure fence being attached to the fuselage portion at a second joining location that is disposed vertically above the cabin floor, a first wing extending in a first lateral direction relative to the fuselage portion and a second wing extending in an opposite second lateral direction relative to the fuselage portion; a first pressure fence attached to the first wing, the first pressure fence defining a first part of the pressure vessel partially defined by the fuselage portion, the first pressure fence being attached to the fuselage portion at a first joining location that is disposed vertically above the cabin floor; and a second pressure fence attached to the second wing, the second pressure fence defining a second part of the pressure vessel partially defined by the fuselage portion, the second pressure fence being attached to the fuselage portion at a second joining location that is disposed vertically above the cabin floor, wherein the first pressure fence comprises a first fence skin and the second pressure fence comprises a second fence skin; the first fence skin extends upwardly relative to an upper wing skin of the first wing and also in the first lateral direction; and the second fence skin extends upwardly relative to the upper wing skin of the second wing and also in the second lateral direction, wherein an upper portion of the first fence skin is attached to a first stringer of the fuselage portion and an upper portion of the second fence skin is attached to a second stringer of the fuselage portion; and the first and second stringers are disposed vertically above the cabin floor of the fuselage portion; and characterised in that the first pressure fence comprises one or more first fence frames and the second pressure fence comprises one or more second fence frames; the one or more first fence frames and the one or more second fence frames are attached to respective fuselage frames; and the one or more first fence frames and the one or more second fence frames extend vertically above the cabin floor of the fuselage portion.