It’s in the “no plans to reopen” stage, someone FOI’d it in October last year:... according to Secrets Of The London Underground. Wikipedia and the net in general seem to have no record of this! Is it closed permanently, or is it just a pandemic thing?
”We can advise that there are no immediate plans to open this entrance,
which has been closed since 23 March 2020 at the start of the pandemic.
This is because a review is taking place to determine the long term
position for the entrance as the building is in need of improvement works
to bring it up to standard.”
Kings cross underground - pentonville road entrance - a Freedom of Information request to Transport for London
The Pentonville Road entrance to Kings Cross Underground Station was closed shortly after the start of COVID 19. Please can you advise whether the entrance is intended to be reopened soon according to its previous hours, of 7am-8pm weekdays; and/or share any documents related to this ongoing...www.whatdotheyknow.com
I didn’t think it was as long ago as 2007 that the station closed at first but then I always remember an argument I had with a staff member at East Croydon when PAYG was first introduced on national rail, I was going to St Pancras International and argued over having to pay extra to go via London Bridge and the tube because the core was shut, and IIRC that was 2010 so the old station must have been shut by then.
Kings Cross Thameslink closed in December 2007 and that's when the St Pancras International Low Level platforms came into use.
The temporary eastern station at St Pancras was much earlier, when the Thameslink network was severed to install the "box" for the new Low Level platforms. North side trains started/terminated at the St Pancras temporary eastern station, south side trains started/terminated at Kings Cross Thameslink. I don't have exact dates but that was around 2004.