Paul Waugh: Part Miss Marple, part Nancy Drew - but she might have missed a trick

The voice, when it finally came, was a surprise. Ever so slightly plummy and donnish, yet eager to chat, Dr David Kelly seemed very relaxed as he talked to Susan Watts, Newsnight's science editor, on May 30.

When the all-important tape of their conversation was played in Court 73 yesterday, it appeared the BBC's prayers for salvation in its battle with the Government might be answered.

Instead of the evasive, nervous figure seen before the Foreign Affairs Select Committee, here was a man happy to chat with the media.

After a dial tone, a phone number being keyed in, and three rings, Dr Kelly answered: "David Kelly". "Hi David, it's Susan here". "Oh, hi!"

Partly out of respect for the dead scientist, partly because it was a strain to hear the tape, the court was utterly silent. Only the mutely twitching screens disturbed the stillness as they fired out transcripts like a Grandstand videprinter.

In this hushed arena was playing the battle of the nerds, the bespectacled defence geek Gilligan versus the bespectacled science swot, Miss Watts, who struck a series of mortal blows. The contest, she implied, was between the mistress of understatement and the master of overstatement.

Armed with a dictaphone, a microphone and some Sellotape (OK, the last bit was 'sexed up'), she came not to praise Mr Gilligan (as her BBC bosses had thought), but to bury him.

Mr Gilligan, on the opposite side of the court, appeared impassive as his colleague set about the differences between their reports on Dr Kelly's doubts about the case for war.

Wearing a pink blouse and blinking nervous tics - apparently developed since giving evidence yesterday - Miss Watts may have appeared innocuous. But beneath the no-nonsense German helmet bob lurked true steel. It soon became very clear nobody, but nobody crosses Susan Watts.

One by one, she blew their reputations away. Mr Gilligan, her manipulative bosses at BBC News, bumbling MPs on select committees and Dr Kelly himself, were all caught in the crossfire. Hell, even the court transcribing service won no mercy (the official transcript was, naturally, inferior to hers).

Newsnight's reporter viewed herself as a plucky sleuth who played by the rules. Her halo slightly slipped only when she admitted she did not tell Dr Kelly the tape was running.

Miss Watts conceded she "missed a trick" in not reporting an earlier conversation when Dr Kelly named Alastair Campbell as being involved in strengthening the dossier on Iraq. For "missed a trick", Mr Gilligan would undoubtedly read "missed a story", but Miss Watts stressed her reporting was always meticulous.

Fifteen-odd minutes later, Dr Kelly's last words "OK, thanks, bye" trailed poignantly off, the tape stopped and the court's computer screens went blank.

Miss Watts said she acted appropriately at all times. The only mystery that truly defeated her was a more mundane one, betraying professional pride, on why Andrew Gilligan's reports got so much more attention from the Government than hers.

She theorised they had not noticed the Newsnight story; they had no quibble with it; or "they were going for me later".

But perhaps the most obvious explanation is not even the mighty State and its spin machine can take on Susan Watts and win. Apparently, when Mr Sambrook found the Watts tape to exist, he smiled broadly. By yesterday's end, the BBC chief's smile had been replaced by a curdled grimace.