Verbal agreement to

I signed a "payback sign on bonus" agreement if I voluntarily quit within two years for my previous employer.

For various reasons, including harassing email's from a fellow employee (which HR said they would fire him if he continued, but they never did - even after a couple additional incidents), I quit eight months prior to the two years.

Before I quit or even before I let my former employer know I was going to leave I inquired about payback of the sign-on bonus.

My manager (in front of others) said this was at his discretion and it was not his policy to seek repayment. Indeed, he indicated he would not require me to repay the sign on bonus if I quit (again, this was in front of two other employees).

Unfortunetly, I should have got this in writing - it's been a month since I quit and started my new job, I was just contacted by the former employer requesting payment of this sign on bonus.

Do I have any recourse at this point?

thanks

P.S. I thought I left on good terms, I was even told I would be welcomed back and please contact them if I ever reconsider working with them again.