You-are-there journalism took a dramatic leap forward last Thursday with the quick availability of cellphone images of the carnage caused by terrorist bombs in London.

Moving video and stills, much of it grainy or shaky, were quickly posted on the Internet and shown on TV. They provided the first, and in some cases only, glimpses of London’s subway system after the first of several bombs exploded during the morning rush in the British capital.

“I think this is a big step into the electronic future,” said Fox News Senior VP John Moody. “The fact that those underground scenes were recorded-and the quality was horrible, they didn’t last very long and they could have used a good producer and director-but you’ve now got a situation where you’ve got millions of potential photographers roaming the streets of Europe, and [Europeans and the British] are ahead of us. What’s that mean? Stringers of the world beware.”

ABC News deployed video cellphones last Christmas to document the holiday travel crush and on Inauguration Day to show what the parade looked like to marchers. “Cellphones just continue the ubiquitous imaging technology that is showing up everywhere,” said Paul Slavin, ABC News senior VP. “In some respects you could say it is the democratization of the news-gathering process.”

“The more video out there, the better it is for all of us,” said CBS News Senior VP Marcy McGinnis.

She was alerted by 5:30 a.m. Thursday and was in her office on Manhattan’s West Side by 6 a.m. CBS News redid “The Early Show” for each time zone.

The broadcast networks had returned to regularly scheduled programming by early afternoon Thursday, but the cable news networks remained focused on the developing story in London.

After NBC’s extended “Today” show signed off at 1 p.m. (ET), Katie Couric moved to the “NBC Nightly News” set, where she co-anchored continuing coverage on MSNBC with Brian Williams for an hour. The experiment was a sign of things to come when covering big stories. “Day in, day out, we have great faith in MSNBC and its team to do what they do. But when there are big stories, everybody understands NBC News needs to be great on every platform we are on,” said NBC News President Neal Shapiro.

For the cable news networks, the story was indeed a big draw. For total day, Fox News Channel averaged 1.65 million viewers, an increase of 82 percent over the comparable day in 2004. CNN averaged 1.09 million viewers, up 81 percent from a year ago. MSNBC averaged 427,000 viewers, up 141 percent year to year.

In prime time Thursday, Fox mushroomed to an average of 2.43 million viewers, a 41 percent increase year to year. CNN averaged 1.33 million viewers, up 2 percent. MSNBC averaged 413,000 viewers, up 23 percent.

By Friday afternoon, news executives were juggling the potential for coverage of Hurricane Dennis at home and the ongong investigation in London.

CNN was planning to move New York-based Anderson Cooper from London to Florida Saturday. Fox News sent five correspondents to London, and Mr. Moody expected them to remain there into this week.

CBS planned to leave some extra people in London through Saturday and perhaps Sunday, pending developments with Hurricane Dennis.