Abstract: A burner for a combustion apparatus, a combustion apparatus comprising such burners, and a method of operation of the same are described. The burner comprises: a fuel input conduit for supplying fuel to the burner; a combustion gas input conduit for supplying combustion gas to a first stage combustion site; an overfire gas input conduit for supplying overfire gas to a second stage combustion site; and gas supply means; wherein the gas supply means is adapted to supply gas switchably between a first mode of operation wherein air is supplied in suitable proportion to both the combustion gas input conduit and the overfire gas input conduit; and a second mode of operation wherein an oxygen containing gas other than air is supplied to the combustion gas input conduit and substantially no gas is supplied to the overfire gas input conduit.