Here

That's a nail bomb, built to kill and wound as many people as possible. It's hard to estimate the size but guessing from the apparent size of the nails, the bottle appears to be perhaps 6-8 inches high and perhaps 2-3 inches in diameter. It certainly wouldn't be hard to hide such a small device on your person (probably uncomfortable with all the nails) or in a backback or briefcase.

I honestly don't know why (or if) the British police didn't want those photos shown or how showing them would hinder their investigation. It seems quite the opposite to me, but then I'm certainly no police investigator.

The deadly nailbombs meant for London commuters
By Jenny Booth, Times Online

Transcript of ABC TV interview
Shocking new images have emerged of unexploded bombs, some packed around with nails, which were found in a car left behind by the July 7 London bombers.

In total, 16 bombs were found in the red Nissan car parked at Luton railway station. It is is believed the car was rented in Leeds by Shehzad Tanweer, one of the four bombers who killed themselves and 52 others in a co-ordinated attack on three London Underground trains and a bus earlier this month.

The sheer number of devices has raised fears that the scale of the July 7 bomb plot was much larger than originally imagined.

The presence of nailbombs graphically illustrates that the bombing cell wanted to inflict the maximum possible pain, injury and risk of death on innocent London commuters, security analysts say.

"You see what is bulging on the sides of the bottle are nails. Many, many nails," said Robert Ayers, a security expert who was shown the pictures by the American ABC News channel last night.

"And the nails are put there so that when the bomb goes off, the nails will tear tissue and kill people in the area. Bombs don't kill by concussion. Small bombs, they kill by the blast effects of fragments of glass or metal, and this is designed to kill people."