Girlfriend's Mum

In between Christmas and new year I was at my girlfriends house.
We snuck upstairs for a quickie and I was fucking my girlfriend from behind on her bed, when her mother walked in.
I thought she was going to start shouting, but instead she began getting undressed as my girlfriend moved off the bed and told her mum she'd wait downstairs.
When my girlfriends mum was fully naked, she got on the bed with me and sucked in my cock.
Claire is definitely what you'd call a mumsy type of woman. She's forty three and a little overweight. But as I found out over the next half an hour, Claire is just as dirty, if not more so, than her daughter.
After she'd sucked on my cock, which was coated in Claires daughters pussy juices, she had me tonguing and sucking on her clit, which is really big.
Then like we'd done so lots of times, we fucked in different positions, with Claire at one point guiding my cock up her arsehole as I spooned her.
At the same time she frantically played with her clitty and had a really strong orgasm, which made me cum up her arse.
We both got dressed after kissing for a while and joined my girlfriend downstairs. And that's when I heard my girlfriend tell her mum "I hope you enjoyed him mum. Happy Christmas".
They'd planned it for weeks I've since found out, and now a few weeks later I've been fucking them both, but not when Claires daughter is around.
Claire is a much better fuck than her daughter and I've come to love sucking on her huge clit. But it's fucking her gorgeous arsehole I love the most, something my girlfriend won't let me do, yet.
Normally I would never look sexually at an older woman like Claire, but she's definitely changed my perception of women her age.