we can date anything from the present day back to about 50,000 years ago. >> in less than 20 minutes, they may solve an enigma that dates back 2,000 years. >> this should just about be finished now. let's just have a look and see what we can see. >> could the waterford cross be part of the cross helena is said to have discovered? >> let's just have a look and see what the result is. we can see that here. >> this relic of the true cross dates from 1100 a.d. >> that's -- >> wow. >> not the age of the true cross. >> okay. it may be around the 1100s. >> it's not the date they were hoping for, but it does reveal the relic's rich history. >> it's very interesting because it seems to match in with the date of the script on the back of the reliquary.