We found a large growth looking a little like an alien brain. It was clearly a fungus but was it edible? Consultation with some eastern European colleagues who professed to be more in tune with the land and self sufficiency (despite being transplanted to this metropolis) yielded ominous results. They declared it best to steer clear and they didn't recognise it from the perhaps vague photos sent through by Tom.
However I had a hunch. A hunch that we had a prized morel in our back yard. Online research showed morels to look similarly pitted and to have a hollow stem. There are false morels which are poisonous but they have solid insides. With trepidation we cut open the growth and to our delight it was hollow.
The next challenge was how to eat it. After worried enquiries by my mother when I told her we were about to eat an almost identified mushroom, we quickly checked where the nearest A&E was (Lewisham I believe). We went for one of 10 easy morel recipes - mushroom and butter pasta. Chopped and added to sweet sweated onions and garlic in butter and served with angel hair spaghetti made for a wonderful meal. Delicious and we are still here to tell the tale.
A word of warning: Do be very careful when identifying mushrooms and if in doubt leave it out.
Other foraged foods that could be found pretty easily are wild garlic (ransoms) and nettles. As usual avoid plants near paths and busy roads to avoid exhaust fume pollution and "doggy messages".