The incident in question occurred in May, but came to public attention this week when police released CCTV footage that shows a jogger on Putney Bridge pushing a woman into traffic, and a bus swerving to avoid her as she falls.
"He categorically denies being the individual concerned & has irrefutable proof that he was in the United States at the time of the incident". Duncan Lewis solicitors issued a statement on Twitter claiming Bellquist was not in Britain when the attack happened in May.
Officers continue to appeal for any witnesses to the incident.
A 41-year-old man was arrested on Thursday morning on suspicion of causing grievous bodily harm, the Metropolitan Police said in a statement.
Mr Bellquist studied at the University of Colorado Boulder and worked for Lehman Brothers before joining Hutton Collins Partners, which owns restaurant chains including Wagamana and Byron.
Police released CCTV footage this week showing the female pedestrian being pushed in front of the 430 bus by a male jogger at about 7.40am.
The bus stopped and some passengers got off and rushed to the victim's aid. He runs past a pedestrian before appearing to shove the woman onto the road as the bus arrives. The woman was only saved by the quick-thinking action of a #Bus Driver, whose vehicle could easily have struck her.
Police described the jogger as a white man, aged early to mid 30s, with brown eyes and short brown hair, wearing a light grey t-shirt and dark blue shorts.