As cancers grow in the body, changes happen in the dna of the body. What happens is those tumours start shedding fragments of that dna into the bloodstream and what the grail this is bbc news with the latest headlines for viewers in the uk testis the bloodstream and what the grail test is able to do is detect those and around the world. Fragments of dna and they have very a call for a rethink over specific patterns associated with them which mean that we can tell Englands Covid tier system but the government defends placing most of the country under tougher whether or not it is likely to be a restrictions after lockdown ends. Cancer and moreover, if it is, where in the body that signal is coming if people do follow the rules, from so we can actually help the if we do make the tiered system doctors to figure out where to look work, then as i say, there is every reason to believe so they can determine very quickly that they could de escalate and go down a tier in time for christmas. Nort