Michael Holroyd Star rating: **** Alison Weir Star rating: **** Nick Davies and Hugh Aldersey-Williams Star rating: **

It was a day when facts were held up for scrutiny like dodgy banknotes. There was no need for a scanner in the case of two of the UK's most authoritative biographers, Michael Holroyd and Alison Weir. Digging equipment would have been more useful for their line of work. At the other end of the information trade, however, journalists Nick Davies and Hugh Aldersey-Williams poured scorn on the facts disseminated by the media, newspapers in particular. In the light of Davies's research, as you read this article please bear in mind that only 12% of its facts have been checked, 80% of its content has come from the PR industry or the wires, and the reviewer is working three times harder than her counterpart 20 years ago. "Churnalism" is the word Davies coins for journalists' outpourings these days, but readers may wish to choose their own.

A degree of intellectual composure missing from his media-bashing event marked Michael Holroyd's writerly session in which he regaled his audience with a synopsis of his new biography, A Strange Eventful History. The story of the relationship between actress Ellen Terry and tragedian Henry Irving, this account also embraces the fortunes of their talented offspring, thus charting Britain's theatrical evolution from Victorian times to the 1960s. A group biography, with six main roles and a supporting cast of eccentric minor personalities, it was, Holroyd confessed, a nigh-impossible venture. Every morning when he got up and faced it again, "I thought this is quite impossible". Piecing together the facts about this family was, he said, more like an archaeological dig than an act of common biography, a process akin to making sense of a jigsaw "which was, firstly, the wrong way round and, secondly, came with no picture". Yet for all its challenges - or perhaps because of them - its therapeutic value for him, personally, has been incalculable. Holroyd spent seven years writing it, partly because of his own grave ill-health. He looked in cheeringly good shape, however, as he confided that "it became extremely important to me to escape from the hospital world into theirs".

Holroyd referred to this project as a "magic carpet", and in Alison Weir's absorbing event there was a corresponding echo of happy flight from reality as she transported her listeners to fourteenth-century England, when Katherine Swynford, John of Gaunt's beautiful mistress and wife, became public enemy number one. As with any medieval figure, there were scant facts on which Weir could base her biography, and much of her work was, she said, an act of inference. Solid spade-work has nevertheless allowed her to build a picture of a woman who appears appealingly modern in her sensuous relationship with Gaunt, and in the degree of control she exerted over her own life.

Weir's interest in Katherine was infectious, and she quoted liberally and vividly from that era's equivalent of the gutter press, namely England's fine monastic chroniclers, who variously reviled her as a witch, whore and she-devil. Swynford couldn't sue for defamation, but were I to print what Nick Davies said of Rupert Murdoch, he certainly could. Suffice to say that as the author of the much-feted Flat Earth News stood to address his audience from a podium festooned with media sponsors' logos, Davies said he was "sad that he Murdoch has his hands on this event and has his newspapers' names plastered all over it". Like a tail-gunner in a spin, he then proceeded to shoot down any faith we might have in the ability of the media in general to report the truth, and warned that things could only get worse. At this point he sounded eerily like one of the headline writers Hugh Aldersey-Williams has been gunning for in Panicology, his tirade against scaremongers.

To that extent it was an inspired piece of programming. From the bemused onlooker's perspective, however, this was a session where neither speaker appeared to be telling the whole story. I, for one, found it hard to tell fact from fiction.