A burner 100 comprising a burner body 110 having a burner chamber with a backing plate 122 and having a burner element received in the burner chamber, the burner element having a plurality of gas nozzles 117 for supplying gas into the burner, the gas nozzles 117 each ending in a tip through which the gas exits and gas nozzle 117, and each gas nozzle being rotatable such that the direction of gas exiting the gas nozzle can be adjusted. The burner has means for rotating the gas nozzles 117 provided on the backing plate and by releasable means for retaining each gas nozzle 117 in a plurality of rotational configurations provided outside the burner chamber. The gas nozzles 117 further comprise first and second parts which are detachable from each other, the first part comprising the tip and the second part being upstream of the first part with respect to the flow of gas into the gas nozzles in use. The burner allows for tuning of gas flow from outside the burner while it is in use.