A turbine section of a gas turbine engine, comprising: a turbine blade having a blade tip; a blade outer air seal (BOAS); and an actuation system for tip clearance control, the actuation system comprising: an actuation ring having a first end and a second end separated by a gap; a blade outer air seal (BOAS), wherein the actuation ring is coupled to the BOAS; and an actuator coupled to at least one of the first end or the second end and configured to adjust a distance (224, 226) of the gap in the circumferential direction such that in response to the gap distance (224, 226) being reduced, the circumference of the actuation ring is decreased, the BOAS is moved radially inward and a tip clearance between the BOAS and a blade tip is reduced; wherein a BOAS gap exists between the BOAS and at least one of a forward BOAS support (308; 408) or an aft BOAS support (310; 410) to allow radial movement of the BOAS relative to the at least one of the forward BOAS support (308; 408) or the aft BOAS support (310; 410); and characterised in that the actuation ring has a first radial thickness proximal to the gap and a second radial thickness distal to the gap that is greater than the first thickness; and in that the actuation system further comprises: a fastener extending through the actuation ring, received by and coupled to the BOAS; and a compressible feature positioned between the fastener and the actuation ring to compensate for uneven flexing of the actuation ring, such that counteracting compression of the compressible feature causes the BOAS to tend to remain radially aligned with the blade tip during actuation of the actuation ring. a turbine blade having a blade tip; a blade outer air seal (BOAS); and an actuation system for tip clearance control, the actuation system comprising: an actuation ring having a first end and a second end separated by a gap; a blade outer air seal (BOAS), wherein the actuation ring is coupled to the BOAS; and an actuator coupled to at least one of the first end or the second end and configured to adjust a distance (224, 226) of the gap in the circumferential direction such that in response to the gap distance (224, 226) being reduced, the circumference of the actuation ring is decreased, the BOAS is moved radially inward and a tip clearance between the BOAS and a blade tip is reduced; wherein a BOAS gap exists between the BOAS and at least one of a forward BOAS support (308; 408) or an aft BOAS support (310; 410) to allow radial movement of the BOAS relative to the at least one of the forward BOAS support (308; 408) or the aft BOAS support (310; 410); and characterised in that the actuation ring has a first radial thickness proximal to the gap and a second radial thickness distal to the gap that is greater than the first thickness; and in that an actuation ring having a first end and a second end separated by a gap; a blade outer air seal (BOAS), wherein the actuation ring is coupled to the BOAS; and an actuator coupled to at least one of the first end or the second end and configured to adjust a distance (224, 226) of the gap in the circumferential direction such that in response to the gap distance (224, 226) being reduced, the circumference of the actuation ring is decreased, the BOAS is moved radially inward and a tip clearance between the BOAS and a blade tip is reduced; wherein a BOAS gap exists between the BOAS and at least one of a forward BOAS support (308; 408) or an aft BOAS support (310; 410) to allow radial movement of the BOAS relative to the at least one of the forward BOAS support (308; 408) or the aft BOAS support (310; 410); and characterised in that the actuation ring has a first radial thickness proximal to the gap and a second radial thickness distal to the gap that is greater than the first thickness; and in that the actuation system further comprises: a fastener extending through the actuation ring, received by and coupled to the BOAS; and a compressible feature positioned between the fastener and the actuation ring to compensate for uneven flexing of the actuation ring, such that counteracting compression of the compressible feature causes the BOAS to tend to remain radially aligned with the blade tip during actuation of the actuation ring. a fastener extending through the actuation ring, received by and coupled to the BOAS; and a compressible feature positioned between the fastener and the actuation ring to compensate for uneven flexing of the actuation ring, such that counteracting compression of the compressible feature causes the BOAS to tend to remain radially aligned with the blade tip during actuation of the actuation ring.