Railway stations serving London's commuter belt remain a prime target for bike thieves, figures show.
Across Great Britain, theft of bicycles from station property rose from 4,500 in 2016-17 to 6,400 last year, a rise of around 42%.
Campaigners and victims said more investment was needed to reduce this "low-risk, high-reward crime".
The Department for Transport said it wanted to improve security and install more CCTV to keep bikes safe.
The BBC's Shared Data Unit analysed crime data from British Transport Police and footfall figures from the Office of Rail Regulation and Transport for London.
It found some 16,725 bikes had been stolen from 1,245 railway and London Underground stations in the past three financial years. Many of the stations with the most thefts were located in London and the South East.
Sam Jones, senior campaigns officer for the Cycling UK charity, said bike theft was "notoriously under-reported".
"Bicycle theft might seem a relatively minor offence - and unfortunately is sometimes treated as such by some police forces - but it is most definitely not," he said.
"It's a low-risk, high-reward crime, with stolen bikes easily changing hands for hundreds or even thousands of pounds on the internet.
"The majority of these bicycles stolen from train stations are not just play things, but are undoubtedly being used as a vital link in someone's journey to work or school."
'I was emotionally attached to it'
Jason Wills, 50, from St Albans, had his bike stolen from St Albans City station in October 2018. He started cycling to raise money for charities supporting his diabetic daughter.
Father-of-two Mr Wills, who works in marketing, commutes to London two or three days a week and cycles three miles to the station from his home.
He locked his hybrid bike at the station on 22 October last year and returned later that evening to find it had gone.
He said: "I was emotionally attached to it because it was a present from my wife and that bike had been to Paris and done Nightrider [an after-dark charity ride in London] three times.
"My space had been violated. I used the bike to raise quite a lot of money for charity to help my daughter and it was ripped from me."
The footage captured on CCTV of the theft was not good enough to investigate it further, Mr Wills said.
"There's a whole approach of getting people to cycle to the station instead of taking their car, and I totally respect that for environmental reasons, but the problem is security at the station," he said.
"In my experience, my bike was probably 10 to 12 metres away from the nearest CCTV camera, but I was told it wasn't good enough for a prosecution."
A spokesman for British Transport Police said: "Unfortunately, bicycles remain a popular target for opportunistic thieves.
"To help prevent crime, we urge cyclists to invest in good quality D-locks and ensure their bikes are securely marked and registered at www.bikeregister.com."
The Department for Transport said it had invested £80m since 2009 to help to triple the number of cycle racks and fund train operators to install CCTV, better lighting, and swipe card entry systems for cycle racks.
In June it announced it would spend £6.8m on 2,300 extra cycle spaces across 48 stations in England.
A spokesman for Govia Thameslink Railway, which runs St Albans City station, said: "We have been hugely successful at St Albans, which is relatively small and yet has the second most bike racks for any station in the country.
"As a percentage of the number of people travelling through St Albans, the rate of bike theft is low - it ranks 213 in the list for bicycle theft."
He said the company planned to create more secure cycle facilities with improved lighting and CCTV as part of a £5m upgrade.
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The Shared Data Unit makes data journalism available to news organisations across the media industry, as part of a partnership between the BBC and the News Media Association. This piece of content was produced by a local newspaper journalist working alongside BBC staff.