An exhaust nozzle for a gas turbine engine, the exhaust nozzle comprising: an outer frame extending along a longitudinal direction; a convergent petal pivotably attached to the frame and extending axially downstream and radially inward from the pivot, radially within the frame; a divergent petal pivotably attached at an upstream end to a downstream end of the convergent petal, and extending axially downstream and radially outward from the pivot; a first sealing hinge arrangement (36,38) between the frame and the convergent petal of the exhaust nozzle, wherein one of the frame and the convergent petal defines a first arcuate part-cylindrical socket (42a,42b) having a first opening along a first cylinder axis which receives a corresponding first arcuate part-cylindrical hinge element of the other of the frame and convergent petal; wherein a first labyrinth seal is formed by an interface between the first arcuate part-cylindrical hinge element and the first arcuate part-cylindrical socket; and a second sealing hinge arrangement between the convergent petal and the divergent petal of the exhaust nozzle, wherein one of the convergent petal and the divergent petal defines a second arcuate part-cylindrical socket having a second opening along a second cylindrical axis which receives a corresponding second arcuate part-cylindrical hinge element of the other of the convergent petal and the divergent petal; whereby a second labyrinth seal is formed by an interface between the second arcuate part-cylindrical hinge element (44a,44b) and the second arcuate part-cylindrical socket (42a,42b), a plenum is disposed radially outwardly from the labyrinth seals, and the plenum extends along a radially outer side of the convergent petal and is configured to receive and provide high pressure air to flow through the plenum and radially inwardly through the labyrinth seals of the first sealing hinge arrangement and of the second sealing hinge arrangement. an outer frame extending along a longitudinal direction; a convergent petal pivotably attached to the frame and extending axially downstream and radially inward from the pivot, radially within the frame; a divergent petal pivotably attached at an upstream end to a downstream end of the convergent petal, and extending axially downstream and radially outward from the pivot; a first sealing hinge arrangement (36,38) between the frame and the convergent petal of the exhaust nozzle, wherein one of the frame and the convergent petal defines a first arcuate part-cylindrical socket (42a,42b) having a first opening along a first cylinder axis which receives a corresponding first arcuate part-cylindrical hinge element of the other of the frame and convergent petal; wherein a first labyrinth seal is formed by an interface between the first arcuate part-cylindrical hinge element and the first arcuate part-cylindrical socket; and a second sealing hinge arrangement between the convergent petal and the divergent petal of the exhaust nozzle, wherein one of the convergent petal and the divergent petal defines a second arcuate part-cylindrical socket having a second opening along a second cylindrical axis which receives a corresponding second arcuate part-cylindrical hinge element of the other of the convergent petal and the divergent petal; whereby a second labyrinth seal is formed by an interface between the second arcuate part-cylindrical hinge element (44a,44b) and the second arcuate part-cylindrical socket (42a,42b), a plenum is disposed radially outwardly from the labyrinth seals, and the plenum extends along a radially outer side of the convergent petal and is configured to receive and provide high pressure air to flow through the plenum and radially inwardly through the labyrinth seals of the first sealing hinge arrangement and of the second sealing hinge arrangement.