A seal assembly comprising: a first component that defines an inner surface; a second component that defines an outer surface and is located radially inward from the first component; a groove defined in the second component, wherein the groove is arranged to face the first component; and a seal ring positioned between the first and second components (22,24) and extending at least partially into the groove; wherein the seal ring defines an outer diameter surface and a first lateral surface adjoining the outer diameter surface, the seal ring is split to define a first free end and a second free end, the first and second free ends (128A,128B) are configured to overlap along a split surface, the split surface extends from the first lateral surface to the outer diameter surface, and the first lateral surface of the seal ring is substantially parallel to a lateral groove surface defined by the groove in the second component; wherein a cross-sectional perimeter of the seal ring is defined by: the outer diameter surface; the first lateral surface; a second lateral surface adjoining the outer diameter surface and located opposite the first lateral surface; an inner diameter surface; a first chamfer extending between the first lateral surface and the inner diameter surface; and a second chamfer extending between the second lateral surface and the inner diameter surface; characterised in that: the location of the split surface maintains a face seal between the seal ring and a first lateral surface of the groove along an entire circumference of the seal ring, including both the first and second free ends (128A, 128B). a first component that defines an inner surface; a second component that defines an outer surface and is located radially inward from the first component; a groove defined in the second component, wherein the groove is arranged to face the first component; and a seal ring positioned between the first and second components (22,24) and extending at least partially into the groove; wherein the seal ring defines an outer diameter surface and a first lateral surface adjoining the outer diameter surface, the seal ring is split to define a first free end and a second free end, the first and second free ends (128A,128B) are configured to overlap along a split surface, the split surface extends from the first lateral surface to the outer diameter surface, and the first lateral surface of the seal ring is substantially parallel to a lateral groove surface defined by the groove in the second component; wherein a cross-sectional perimeter of the seal ring is defined by: the outer diameter surface; the first lateral surface; a second lateral surface adjoining the outer diameter surface and located opposite the first lateral surface; an inner diameter surface; a first chamfer extending between the first lateral surface and the inner diameter surface; and a second chamfer extending between the second lateral surface and the inner diameter surface; characterised in that: the location of the split surface maintains a face seal between the seal ring and a first lateral surface of the groove along an entire circumference of the seal ring, including both the first and second free ends (128A, 128B). the outer diameter surface; the first lateral surface; a second lateral surface adjoining the outer diameter surface and located opposite the first lateral surface; an inner diameter surface; a first chamfer extending between the first lateral surface and the inner diameter surface; and a second chamfer extending between the second lateral surface and the inner diameter surface; characterised in that: the location of the split surface maintains a face seal between the seal ring and a first lateral surface of the groove along an entire circumference of the seal ring, including both the first and second free ends (128A, 128B). the location of the split surface maintains a face seal between the seal ring and a first lateral surface of the groove along an entire circumference of the seal ring, including both the first and second free ends (128A, 128B).