Credibility isn't binary. What's credible for one news organization says nothing about what another organization/journalist/court-of-law-in-the-UK believes is credible.
There are many more ways to establish credibility - does your story add up, do you know things you wouldn't without having inside info, can the journalist verify that info with a known insider, have you been a credible source in the past, are you personally known to the journalist, are you a known person in the community, do you have a proven connection to the primary source, etc.
There are many more ways to establish credibility - does your story add up, do you know things you wouldn't without having inside info, can the journalist verify that info with a known insider, have you been a credible source in the past, are you personally known to the journalist, are you a known person in the community, do you have a proven connection to the primary source, etc.