Disclosed is a swirler for use in a burner of a gas turbine engine, the swirler comprising a plurality of vanes arranged in a circle, flow slots being defined between adjacent vanes in the circle, each flow slot having an inlet end and an outlet end, in use of the swirler a flow of fuel and air travelling along each flow slot from its inlet end to its outlet end such that the swirler provides a swirling mix of the fuel and air, at least one vane having an edge adjacent an inlet end of a flow slot configured to generate within the flow slot one or more flow vortices that extend along the slot thereby to enhance mixing of the fuel and air travelling along the slot.