I have picked them out with a sharp scriber by using the point to jag into the metal of the key tail but if it has broken off too far down you may need the services of a locksmith. There are mobile locksmiths around depending on where you are at present.

Get a fine tooth hacksaw blade, and grind the back side down so that you have a fine, narrow snout with teeth left. Make sure that the teeth are pointing backwards. Slide the blade under the key, let the hacksaw teeth bite into the key stub and gently pull it back.

No thank goodness.  Thanks for your reply June C

There are very fine pointed tweezers (the type used by eye surgeons) they have a positive grip as do surgical clamps. I know these are normally used by Drs and Nurses but some people (like me) do have them in their First Aid kits.