After the rain...an orchid appears

...in a dry old pot

Suddenly after a deluge of rain this past week, the garden has come alive. One of the larger pots next to the summerhouse has a pieres 'Forest Flame', some meandering periwinkle and at some point there had been dwarf tulips in the pot, which had never really come to much. Imagine my surprise when a couple of days after the heavy rain I noticed the following flower appear.

Over the years we had seen the leaves come up and assumed it was a remnant of the tulips planted over 10 years ago, and hadn't flowered. 
At first I thought...No..it can't be an orchid...can it?!
Then after posting the photograph on Facebook, all those who replied suggested some form of orchid...someone had mentioned a bee orchid, but I thought it was something more common.
A few searches later and I have come up with an early marsh orchid.
Here are some more photographs taken this morning. Let me know what you think it is...I would really like to find out for sure.
Next step is to learn how to keep it going over the years. 
In the meantime...I am watering the plant every day...if you know if I need to do this let me know.