A diverter assembly for a tree of an oil or gas well is disclosed, the assembly comprising: a lateral branch having first and second branch bores with the first branch bore having a first port and the second branch bore having a second port, the first branch bore forming part of a first flowpath to and from a production bore of the tree and the second branch bore forming part of a second flowpath to and from an export line; a diverter having first and second internal passages, the first internal passage communicating with the first port and the second passage communicating with the second port; processing apparatus disposed between the first internal passage and the second internal passage; and the diverter and processing apparatus communicating the first flowpath with the second flowpath.