I spent last Sunday with a group of people who walk back and forth over ploughed fields picking up broken bits of pottery and stone. No, they're not crazy - they're the "East of Sutton" survey team and what they're looking for is the discarded debris of past civilisations.

The first surprise is that there are any fields in Birmingham at all.

But the north-eastern part of the City boundary around Over Green, Minworth and Peddimore is good farming land to this day - and so it has been for thousands of years.

All that time countless generations of farmers have dumped their broken crockery on the manure heap and then spread it over the fields.

That's what today's searchers hope to find. The stuff is worthless but gives to clues to how and at what period the land was being used.

Prehistoric, Roman and medieval pottery all come in specific types which an expert can identify. The trick is not being deceived by bits of stone or modern pottery.

At the end of each session, finds are examined and the junk - which is usually most of it for beginners - thrown away.

The large field which we did produced about a dozen bits of medieval pottery and one prehistoric flint. The group has so far covered 46 fields and has many more to do.

Gradually they're building up a picture of where people were living in prehistoric, Roman and medieval times.

If you're interested in taking part or finding out more about the group, which also include identifying ancient earthworks contact Terry Jones.