Former world champion Idowu made a good start to a season he hopes will climax with Olympic gold medal on home soil with victory in the triple jump with a leap of 17.24 metres.
"I am in great shape," said the Londoner.
"My timing was slightly off and my technique was not perfect, but this was the first one of the year and I feel great."
If the former world champion was trying to lower expectations about his chances of regaining the Olympic title he relinquished through injury in Beijing, he went about it in the wrong way in front of more than 40,000 screaming compatriots.
A blistering start put him well clear by the halfway mark and he raced across the line half a metre ahead of American David Oliver (13.13) before ripping off his shirt in delight at the first sub-13 second time of the year.
"I am really happy. I executed well, I ran my own race and wasn't thinking about the others. I just did what I had to do and I won," the 28-year-old told reporters.
"The crowd came out despite the wind and rain and I really enjoyed the atmosphere. I had to put on a fantastic performance for them."
Former world record holder
"I did technically well so I'm happy," the Jamaican said. "I felt good, it went well but it was raining so I didn't push too hard."
Jeter came at the Jamaican three times down the home straight but Campbell-Brown, who will be going for a third straight gold in the event in London, had enough in the tank to see her home in 22.50 seconds.
"The more I win the more confident I become," she said. "This was my first 200 metres of the year and I have a lot of work to do but I know from how I felt in this one that each race will get better so I'm just praying for good health."
World indoor champion
"I am very, very happy," said Dibaba, the 21-year-old sister of Olympic 5,000 and 10,000m champion Tirunesh. "I felt strong and I had a good feeling that I would win."
Heavy rain made a lottery of some of the field events.