He's a pathological liar

I would always confront lies. Just tell him that his lies make it difficult for you to believe anything he says.

Those poor women. I think the best thing you can do is support them.

You don't have to put up with his lies and deceit; you could call him out on it every time you catch him doing it. You could quiet calmly tell him that you know he's often/sometimes parsimonious with the truth and you don't want to hear any more lies and so he should think carefully before telling you anything that could be untrue because you're not prepared to accept it any longer. You wouldn't accept it from a friend would you? So why from him?

I remember you posting before.
Was he about to get counselling at that time?

Really, his problems are too complex for you to try and deal with, but I appreciate there's often no alternative.

He is obviously unwell - and has been for a considerable time. Leaving may be a positive change for him, his wife and daughters. It may allow him to begin recovery.

You say he has everything - but he doesn't even have his (very important) mental health. The lies could be a symptom of his pain and distress. Give him all the support you can.

He hadn't got everything, he's lost two families because of his mental health issues. If only there was a pill to put it right but of course there isn't. It's hard I know. ?

Out of the wreckage your son is making of his life you have managed to construct and maintain a good, supportive relationship with both his wives and his three daughters.

He seems to have complex problems and the support he he has received has not worked, You have acknowledged that he is a pathological liar, and I don't think you can do any more than you are at present to help him until he acknowledges his problems.

Does he have any sort of relationship with his father?

You know your son best so I won’t tell you what you should do, but I suspect the reason you’re asking is that you feel you must confront him when he lies.

If that’s the case then do so.

Judging from the time scales you mention britgran it seems unlikely there will be much change in your son's behaviour. It must be very difficult for you to see someone you love behaving like this.
He will always be your son and you love him but you hate what he is doing to his families. I think you should say what needs to be said in a calm, controlled way and see if he will get some help with his problems.
Your son needs to see the need for change before he will do anything so all you can do is support the people affected by his behaviour. You are clearly doing that, I sympathise and understand how hard this is for you.

You sound a good person for you two daughter in law to have and I commend you for that it’s not easy to admit your adult children’s faults
I would definitely call out his lies in as non confrontational way as possible and stay supporting the two families he has left
He obviously has deep rooted problems long before the bulimia because that was in response to something

Hopefully he may be able to get some counselling for the root problems Voice this lockdown is over he dies need help

Thank you everybody, I can always rely on good advice here, I turned against him when he left his first wife and I'm trying so hard not to go down that road again, it was a big mistake that I hope I have learned from, his first wife met someone else who didn't want her associating with us so she cut ties with us along with her children from another relationship I was devastated even though I understood him. My son gets on with his father but it would cause all sorts of problems if they fell out with both of them being of the same temperament so my husband tends to keep quiet, my other son has no time for his brother and considers him to be a complete idiot, he doesn't understand the mental illness but saying that they didn't get on as children when I said he has everything I realise he doesn't have it all, but in all honesty who has everything ...it was a figure of speech, but he has a good job, earns good money, lovely home, lovely wife, delightful children and parents who love him. I feel such a failure as a mother, I will take all your advice on board

britgran, just catching up with this. There are some supportive comments which I agree with.
Its so good to read that you have managed to maintain good relationships with your son's ex partners and your grandchildren.
I understand why some say you should try to offer as much support to him as possible and agree. I'd add, don't do that to the exclusion of your own needs and health. Adult children with long lasting emotional/psychiatric/psychological mental health problems are such a worry to their parents. He needs to be responsible for himself, to seek appropriate help and support. You need to look after yourself.

If it was some time ago that he received counselling, maybe he needs a referral to a specialist clinic again.
Only he can do this - but if he is miserable enough he may be prepared to consider this again - and you can offer support if he seeks help.

He's clearly very unwell which has gone on for a long time so will take all the longer to put right.
What was the root cause of his bulimia ?

You are not a failure britgran its not your fault that your son is ill. You have supported him and his family very well it seems.
Remember to look after yourself in all this as Iam64 said.

He was an overweight teenager and suffered terrible stomach pain from age 9 , we were constantly being referred to the hospital where it was decided it was stress related,I made a real nuisance of myself so lots of tests were carried out but nothing was found, when he was 18 he was admitted to hospital, he couldn't eat and lost lots of weight, he was thrilled to bits, I believe this was when the Bulimia started, they found stones in his Bike Duct when he was 19 this was the cause of 10 years of dreadful stomach pain, they hadn't looked before as it's rare in a youngster, I was not a happy bunny