Colleagues Dirty Wife

My colleague invited me round to his home in between Christmas and new year.
We had a few drinks, then he half jokingly mentioned to his wife that I have a big one.
She asked how he knew and my colleague told her I'd fucked one of the women at work, and she'd let everyone know.
I'd gotten embarrassed by this point, but not as embarrassed as when his wife said "Why don't you let me suck it for you".
This is the truth. I genuinely didn't know they were occasional swingers and I honestly thought it was just a drink.
Even so I ended up with my colleagues wife sucking on my dick as he tongued her pussy and arsehole from behind.
I didn't fuck her that night, but I did cum all over her tits and watched my colleague fucked his wife from behind with his small cock.
However two days later with my colleague apparently out at his golf club getting pissed, his wife messaged me.
We spent the entire afternoon licking, sucking and fucking and trust me my colleagues wife was extremely dirty. She even tongued my arsehole after I'd cum in her mouth, spreading my cum inside my rear hole.
We've fucked three more times since then, and each time the sex has been amazing.
I asked her on the last occasion if her husband knew about us and she said no. When I asked why after what had happened Christmas time, she said "Because when you left that day he said that was the last time".
I'm not sure if it's because he has a small cock, but from what my colleagues wife has told me, them actually fucking during Christmas was only the third time in months.
She definitely wants and needs sex more often, and for now I'm going to keep on fucking the forty three year old.