So what would you do?

Starting to see it mzz - I overlooked that it's a deferred final salary pension - so as soon as he hits 60 he can "cash it in" take the lump sum and take pension payments and carry on working and contributing to other pensions.
Your post has opened my eyes to the fact that my ex's deferred final salary pension payable at age 60 will soon be available to him on that same basis - once he's 60 - even if he doesn't "retire" and continues with his current work, the deferred pension is as good as ready money.
That could be really useful when he applies to reduce my maintenance.

You are being reasonable taking it all.
Reverse think on this he agreed that after the lump sum was paid he would have £0.the fact that the lump sum is now £81k rather than £47k is irrelevant.He signed that he was happy to accept £0 of the lump sum.
Stick to your guns he signed the Consent Order that's it.Don't let him complicate the issue.
If he's pension had been £47k lump sum and he was going to receive £16k a year rather than the £14k he expected you can bet your boots he wouldn't have given you the extra £2k a year.
The ultimate point his he weighed it all up and said you could have all the lump sum if he's miscalculated tough.
If you felt really generous maximum £17k 50/50 split of the extra £34k over the original figure estimated. £81k - £47k = £34k/2 = £17k each maximum at your discretion don't agree to him messing about with the consent order at all.
all the best
Pete

Have you made enquiries as to what amount of penson £81K will buy you?

And how much, realistically, are you likely to be able to add to that over the next 10 years? Is your income in retirement likely to be £12,000 p.a.? I would guess that £81K would produce a pension of between £2,500 and £5,100 p.a. depending on the annuity you buy. If you are 50 now, you won't be entitled to a state pension until you are nearly 66 and (on current rates) that would give you a further £5,500. So you'd have perhaps £10,000 in total, wheras even on the lower than expected figures, he'll have £12,000, rising to around £17,000 once he reaches 65 and can claim his state pension.

I would question wehther it would be sensible, or reasonable, to give him extra.

I don't think it would be at all unfair or unreasonable for you to keep the whole of the lump sum; after all, had it worked out that the pension payable was much higher than anticipated, do you think he would have been falling over himself to give you extra?

if you do feel you want to give him something then I would limit it - maybe £5,000 to equate to 50% of the shortfall on the anticipated figures, for 5 years until he is able to claim his state pension.

But do your own sums to see what position youare likely to be in, first, and decide whether you can afford it. After all, whatHaywaythelads says is absolutely right. He agreed to have no share of the lump sum, He hasn't lost out, it's just that you have had some good luck.

If the asset you'd kept was the house, and it had unexpectedly gone up in value, would he be asking you to pay him extra from that, too? What if the pension lump sum had turned out to be lower that you'd expected? Would he have paid you a lump sum to make up for it?

Thanks for all your comments and views. I really appreciate how much care and thought goes into so many wiki-postings.

Well, I weighed things up and decided to split the lump sum with him 2/3rds to me and 1/3 to him. So I get about 54k and he gets 27k. I'm 7-9k better off than I thought I would be and he can do what he likes with the 27k to try to bring his pension back up to what he'd hoped for / pay off some of his mortgage or whatever.

That might sound bonkers but he is ending up with over £3k less pension p.a. than we both thought he'd get and that sense of financial security is really important to him. His work is drying up in the current climate and he took on a big mortgage when we split up, with not long to pay it back.

I've always been happy to live on my wits, which may yet be my downfall but I've survived up to now.

Just in the last few years I've been earning a good salary and I'm with a wonderful new man (whose XW is now my XH's 'companion' - but that's another story!. He won't retire with very much either but we've got a big veg plot and some chickens so we won't starve.

TBagpuss - wow I wish I was back at age 50! - but I reckon I've still got 10 years to accumulate some savings / pension and can probably get somewhere close to XH's £15k by various routes.

So maybe not a sensible decision but one I feel right about taking. Watching my partner being dragged through a wildly expensive divorce that gifted about £50k to the legal profession - and left his XW worse off than his original offer to her - makes me glad that XH and I didn't take the same route - there would have been much less for either of us that way.

Thanks for listening.
Mzz

I think your feeling right about the decision is the most important thing