Jonny stopped at the side of the road but Alistair, who had been running comfortably in third, put his arm around his brother and all but carried him along the final few hundred metres and then pushed him across the line.
By finishing second with Mola in fifth, it was the Spaniard who took the title by just four points.
Alistair suffered similar drama in Hyde Park in 2010, and he told the BBC: “It’s an awful position to be in.
“If he’d conked out before the finish line and there wasn’t medical support it could have been really dangerous.”