Pull out the 2 silver pins and it pulls apart, apply silicone grease to the o rings and re assemble.
Notes - inside are two ceramic plates that control water flow make sure they are seated properly before re assembling.
IMO the pins are too short they are hard to remove and get damaged by pliers/mole grips I brought a bag of 100 ( £1.25 off ebay )that are 12mm long and can be removed and reassembled earlier than the originals
Darran