As the first report of the accident came in, Burton was sitting in his of rice on the top floor of the building. Immediately, realizing the seriousness of the whole incident, he gave over to the investigation a ground floor room with a small waiting - room leading off it and took charge himself, leaving his second -in -command to take over all other cases. He interviewed the first witness almost at once, making sure that every thing was done that could be done to put him at his ease. However, the wit ness was evidently nervous and Burton took considerable pains to go over the ground thoroughly, choosing and checking each word to be precise and taking the man's statement down in longhand himself. The witness had called the police, he'd waited until the ambulances began to arrive then when the first police car arrived on the scene he'd been asked to report to the station which is what he had done. Burton explained that regrettably it would be necessary for him to go to court because of the serious nature of the disaster. More he could not say at present. He'd be grateful if the man would stay in contact with the police. When he had gone, Burton put his head in his hands and considered be fore asking for the next witness. He couldn't be regarded as a hundred per cent witness because he had been behind a wall when the explosion occurred. But in spite of his nerves, Burton had the impression that he was reliable, not afraid of incriminating himself and a fairly accurate observer. Well, there would be other accounts and no doubt all these would be slotted into place like a jigsaw and the whole picture would become clear. He raised his bead and pressed the buzzer on his esk. 'a hundred percent witness' most probably means ______.