It all started when my F-I-L left his then 50yr old wife for a 'girl' half his age. The M-I-L then went through a confidence crisis, though for a woman as attractive as her with such a well-toned and looked after body there was no reason for her to do so. After her first year of being single had passed, the M-I-L called at ours one sunny Sunday morning and announced she had booked a holiday to the Algarve for herself, the wife and I, plus of course, her delightful two grandchildren, aged 9 and 12. The reason for this she said was enough was enough, time to get on with the rest of her life. We'd long thought she was waiting for hubby to come back to her after his fling. We were on our second night when the wife had drank enough and suggested we called it a night. The M-I-L wanted to stay out so the wife went back to the hotel with the kids and it was 'my job' to look after the M-I-L. I must say right now, in the previous 16yrs of knowing her, there'd never been the slightest hint, suggestion or look regarding anything untoward between the M-I-L and myself. We had visited a couple of bars and were feeling very merry, when very innocently, a waiter mentioned that we looked like a very happy couple, to which the M-I-L responded 'if only'? On the walk to the next bar I asked her what that comment meant and she suddenly stopped and kissed me with such passion that my hands were all over her and there we were, mother-in-law and son-in-law snogging in the middle of the street like a pair of teenagers. When we stopped kissing there was an uneasy few seconds, we then sat at the next bar where we continued where we'd left off in the street. My hand was now up her skirt with a finger in her soaking wet pussy and she was rubbing my rock hard cock from over my shorts. I asked her did she want me to make love to her.....her eager response was no, I want you to fuck me. We went down towards the secluded beach where I had the absolute pleasure of removing the clothes from my sexy, gorgeous mother-in-law, bending her over a wall and fucking her doggy-style where I proceeded to call her a dirty little slut and cheap whore before exploding loads of spunk into her. She loved the name-calling. We walked back to our hotel and instead of us feeling awkward or even mortified with what we'd just done, we were remarkably at ease with it, and each other. TO BE CONTINUED................