P&O Ferries said it was "delighted" to help an obese Frenchman stranded in London after Eurostar refused him entry on to a Paris-bound train.
Kevin Chenais, 22, was denied entry on to a Eurostar train as his lack of mobility would have breached strict safety regulations.
The incident was the latest setback for Mr Chenais as he bids tor return home to eastern France, after British Airways originally refused to fly him home from America.
A P&O Ferries spokesman said: "We're delighted to help. It's not difficult for us. We are used to carrying ambulances across the Channel, so we are set up for this type of thing.
"It's difficult to imagine the frustration that this gentleman has gone through. But for us, it's very straight-forward as we are set up to carry people who have medical needs."
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Ms Leadsom has received the backing of Ian Duncan Smith, the former work and pensions secretary.