OP my ex husband did this to me.I wanted the divorce,I sorted all the paperwork out for us both or he never would have done anything about the divorce.
He was in a commited relationship(so he said)and he let that women look into IVF to have children with him,he'd met all her family,they'd set the date,started booking and paying for everything,she'd got her wedding dress,told everyone they were getting married,chose her bridesmaids and what they'd all be wearing they were that far in they were sorting out they're Hen and Stag do's.
The dishonest Bastard still hadn't put the divorce papers in,every time I see him once a week to pick up the kids he'd tell me he'd put them in and he'd spoke to someone and it was all being sorted it was all a lie.
I found out the truth when I was talking to him about it in front of our sons and when he'd left our oldest told me Daddy still had that envelope in his old coat Mummy in his car.
The next week I walked straight past him went into the boot of his car took out the papers.His answer oh I'm sorry I was sure I'd put them in I'll do it now blah blah blah.I caught a bus straight into town and handed in the paperwork myself.
A few weeks later I found out ex and his partner had split up after mammoth rows,he didn't want to marry her so used the fact that he wasn't divorced yet and then I found out the bastard blamed me.
He's re-married now with 2 more children but he still trys to flirt with me and he's told my family and his family only a couple of years ago that he'd come straight back if I'd have him.There's not a chance in hell.
Just be careful OP that he's not like my stupid ex husband.