The railways have been hit by long delays after a series of signal failures and planned station closures.
Trains between Lewisham and Charing Cross are being delayed by up to 50 minutes due to signalling problems, with disruption expected to continue until at least 4pm.
The issue has been going on since this morning.
Meanwhile there are no Southeastern services calling at Cannon Street until Thursday.
Communications officer Andrew McGill, 31, said his journey from Lewisham to London Bridge, which was scheduled to take 10 minutes, lasted 53 minutes.
He told the Press Association: "We were packed in like sweaty sardines. A young man next to me was on the verge of fainting and it was only thanks to passengers using newspapers as emergency fans he remained conscious.
"The driver was apologetic but in the week London Bridge reopened this morning's chaos will not inspire confidence among commuters that the rail infrastructure can cope with demand.
"It was the worst commuting experience I have had in over two years living in London. There were a lot of very hot, very angry people."
Commuters across south-east London and north Kent have taken to Twitter to vent their struggle.
.@CliveEfford my husband is still on train that left New Eltham at 8.22 and hasn't left Lewisham yet! Who @Se_Railway can be held rspnsible?
— hannahbflynn (@hannahbflynn) August 31, 2016
@Se_Railway an hour into my journey from Catford Bridge and still not even at London Bridge. What has caused the signal issues please?
— Tom Stabb 💩 (@tomstabb) August 31, 2016
@Se_Railway 1hr from Woolwich to Lewisham on 8:08, stuck outside Bermondsy somewhere still. What's goin on?? Joke
— Sam Heffernan (@sam_heffernan) August 31, 2016
I'm very lucky not to be commuting at the moment - my partner was stuck on a @Se_Railway train for over an hour this morning. #southeastern
— Nigel Fletcher (@nigelfletcher) August 31, 2016
Dear police, we're being held hostage near St John's station by @Se_Railway. Please send help. pic.twitter.com/khWxZ6g0fg
— David Eckhoff (@theroyalfactor) August 31, 2016
A spokesman for NR said: "We are sorry for any delays people are experiencing travelling into work this morning.
"A signalling problem has caused delays to and from Charing Cross. We are unable to use platform nine for trains coming into London Bridge. Engineers are on site and we are working to resolve the problem.
"We also had a signalling problem in the Lewisham area. This has been resolved, but there are still significant delays as the services recover."
Rail operator Southeastern had previously "strongly recommended" that passengers should consider changing their usual journey to work this week.
"We will not be able to run as many trains as normal and our services will be very busy," the company warned.
Earlier this morning a man was accidently pushed onto the tracks at Catford Bridge station.
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