This happened when I was 15 back in the sixties
I was 15 and my girlfriend Barbara was 14, both of us living with parents so privacy was difficult. We had reached the stage of mutual masturbation and found a way to enjoy this outdoors without getting caught.
We would go for a walk during the autumn evenings when it was dark along a lane which was only weakly lit and ran behind our estate. Both of us wore knee length coats which buttoned down the front.
We each had an arm round the other's waist and the other hand inside their coat. Under cover of the coat Barbara would unzip my trousera and get my cock out and slowly wank me as we walked. I had my hand in her coat and would lift her skirt above her stocking tops untl I could slide a hand inside her knickers and then part her delicious pussy lips and rub slowly at her clit.
Thus entwined we would walk along the lane mastutbating each other and only had to pull a hand out if we passed anyone.
One night a policeman stopped us and shone his torch over us but could see nothing because of our coat. Luckily he didn't look closer as my cock was out and Barbara's skirt was hiked up above her knickers.
When she made me come she would catch what she could of my spunk in her hand to stop my coat from becoming stained inside.
The excitement of doing this so publicly and both being exposed beneath our coats added a lot of spice to our young fun.