Officially only since 2016, but it was certainly possible unofficially much earlier.
The line closed in 1959, requiring trains from Sheffield to Lincoln to divert via Gainsborough, but most of it, except the viaduct itself, re-opened in 1968 to serve Cottam Power Station on the Nottinghamshire side of the Trent, and Torksey oil terminal on the Lincolnshire side. (The oil terminal closed in 1988 and the power station in 2019).
When Lincoln power station closed in the 1970s my late father was seconded to Cottam, which meant a 20 mile journey each way via the A57 toll bridge at Dunham. On several occasions the Trent flooded the approach roads to the bridge, requiring a detour via Gainsborough (27 miles each way) or the Newark bypass (36 miles each way, but on faster roads and avoiding Gainsborough's town centre). What he and his colleagues actually did when the A57 was impassable was to drive the 13 miles to Torksey and walk across the old viaduct.
As a secondee he was allowed to claim travelling expenses. But the expenses people insisted that they had to pay him for the official route via Gainsborough if the A57 was closed, as they couldn't condone him and his colleagues trespassing on the viaduct.