I am 42 and last Monday I twice noticed really black motions in the toilet pan after "going". Can I safely ignore this?

No. Black motions can be due to drinking red wine or taking iron pills. But they can also be due to intestinal bleeding. So you must see your doc in the next couple of days. Please take along a teaspoon-sized sample of bowel motion for testing. Your surgery will give you a suitable container if you ask beforehand.