Swimmer Fran Halsall ignored a dose of 'Delhi Belly' to win a shock women's 50 metre butterfly gold and kick-start England's Commonwealth Games Ashes battle with rivals Australia on Tuesday.

The 20-year-old Halsall turned and checked the giant screen to see she had edged Australia's Marieke Guehrer by 0.03 seconds and then punched the air in delight at winning England's first gold of the Games.

"It was just on who got the touch and I had a pretty good finish so I was really happy and a bit shocked to be honest," a beaming Halsall, who was suffering from an upset stomach, told reporters.

"I wasn't really planning on getting the gold in that one," she added.

The slight Halsall, European 100m freestyle champion, was towered over by Guerhrer and third placed Australian Emily Seebohn as the trio collected their medals and the jovial winner could not resist a friendly dig.

"It was really nice to see the England flag at the top and two Aussies underneath," she joked, still dripping from the pool.

There was little time for Halsall to savour the victory as she jumped back in the pool to compete in the women's 100m freestyle heats.

"It was a little bit stressful afterwards as I had medal presentation people pulling me around, drugs testing people pulling me around and I had to get back for my other swim so it was all quite frantic trying to get prepared," she said.

Games organisers have been trying hard to appease athlete concerns over health, security and accommodation but Halsall said she was just concentrating on winning further gold medals.

"It is a lot different situation here with all the different things like buses (taking) 40 minutes here and back (to the village) and a bit of Delhi-belly (upset stomach) going on so we'll see how it goes," she said.

"I don't want to be beaten in my main event that is for sure. I have seen the doctor about some cream as it hurts as well, although you probably don't want to know that," she laughed.

Should Halsall prove victorious in one of her other five events, she will be better prepared to sing the anthem after looking somewhat red-faced when the hymn Jerusalem rang out.

"It was nice but I don't really know the words to Jerusalem as I was going to sing 'Land of Hope and Glory'."