Just some more info....
*Talk with any decent mechanic with experience on common rail diesels and they will tell you adding an additional fuel filter/water catch wont have any negative impact on your engine.
*Others that say otherwise have zero to very little knowledge about how a common rail diesel functions. (such as the technical/service department of a vehicle manufacturer or dealership)
*Vehicle manufacturers are always going to state along the lines of "we dont support any non factory approved modification"
*Around 80% of fuel flow delivered to a common rail engine gets returned to tank.
*Typically a one fuel filter setup on a common rail diesel will filter around the 5 micron mark, a 5 micron filter is often called a "secondary" filter. Filter that do around 10 micron or bigger are considered a "primary" filter. So if only using the one filter setup you use a "secondary" 5 micron filter.
*So if you fit a filter after the one stock filter, you need a filter that does smaller than the stock filter, say around 2 micron and ideally a water trap. If you fit a filter before the stock it needs to filter larger particulate such as round 10 microns and again ideally a water trap.
*A Defender TDCi 2.4 does not have a in tank fuel delivery pump (previous TD5 and later 2.2 do have a in tank fuel delivery pump).
*The one way breather on a Defender TDCi in just above the top of the fuel tank and are prone to either blocking and causing "venting" through the fuel lock cap OR are prone to sticking open, in both cases water ingress is possible.
*When I fit long range tanks to the Defender TDCi or do any work on the fuel tank, I route that pesky one way breather to just behind the filler cap (nice and high away from water/mud ingress hopefully).
**The basics I religiously state to customers....
*Service every 10,000kms which always includes oil, oil filter, air filter AND FUEL FILTER.
Regards
Daz

