The irony is Teabay that it's taken him leaving me to see him for what he really is - a woefully belated lightbulb moment following 20 years of thinking perhaps it was me!
Natsku I don't even know where to start but long story short (ish) is that he left at the end of January after a five minute conversation telling me he just wasn't "feeling it" Soon transpired OW was involved although up until quite recently he's been denying this (despite moving in with her!) preferring instead to blame me and the "major problems" - which he failed to communicate to me - within our relationship. Strange that with my multitude of supposed shortcomings to cite he chose to base the divorce petition on pure fabrication 
Anyway, I digress. Over Easter he told DS (10) about OW, although he claimed it was a new relationship, and subsequently duped him into spending the day with them and her DD against DS's wishes. DS was very distraught when he came home and said STBXH had paid more attention to them than to him and had carried OW's DD around all day. He asked if his dad now loved her more than him 
Within a couple of days of this debacle X also decided, in his infinite wisdom, to deposit our 14 year old daughter in a strange city 90 minutes from home with her 17 year old boyfriend (who he'd met once, briefly) unsupervised for 36 hours.
Following this weekend's contact DS has once again returned in tears as X spent the majority of their time together messaging / Face Timing / phoning OW, even tracking the progress of her bike ride on Google Maps and then bringing DS home at the earliest opportunity. But only after having gone shopping in front of him en route to buy stuff to bake a cake and cook roast dinner for OW and her kid. DS came home and asked to see a counsellor.
Then yesterday he told DS he wasn't able to see him on a specific weekend as he was taking OW to a music festival. Cue more tears.
Incomprehensibly, he seems utterly oblivious to the damage he's doing. I had told MIL about DS wanting to talk to someone and she relayed this to X who then text me to say he wanted to be involved in the counselling to help DS understand what was going on! Ummm, that would be that he's a selfish, deluded fuckwit.
That wasn't really short at all. And it's only even the tip of the iceberg. Sorry. I'm just raging.