Scam mail has been arriving in Britain's letterboxes in a steady stream for years, targeting the most vulnerable and robbing many of their savings. But what role does Royal Mail play in getting it to your front door? Panorama's Tom Heap reports.
Last year alone, Royal Mail delivered 1.7bn pieces of junk mail to British homes.
And while local authorities grapple with the cost of disposing of the masses of paper involved amid squeezed budgets, others worry about a darker side of the Royal Mail's letters business - the delivery of scam mail.
Scam mail letters are sent by fraudsters from overseas countries who try to persuade people to part with money on false promises of winning cash prizes.
If a victim replies to one of these "tempter letters" their name can end up on a so-called "suckers list" of vulnerable people that can then be sold on to criminals all over the world.
These cons are estimated to cost their victims £2.4bn a year and have prompted one MP to call for a change in the law so that scam mail can be intercepted as it enters the UK.
Once scam mail has entered the UK postal system Royal Mail have a legal obligation to deliver it.
But a BBC Panorama investigation has highlighted that Royal Mail owns 33% of the Netherlands-based company that is enabling large amounts of the scam mail to get into Britain.
Spring Global Mail handles vast amounts of mail for legitimate international business, but it is also being used by scam mail fraudsters. The balance of the company is owned by the Dutch postal service, Post NL.
Worrying for some critics is the "local look" service offered by Spring Global and Royal Mail whereby letters from abroad bear the Royal Mail postmark and have no trace of their overseas origins.
Fraud investigator Detective Chief Superintendent Steve Head of City of London Police said the Royal Mail logo is seen by some victims as a stamp of legitimacy.
Most scam mail comes from abroad but carries a 'local look'
"I think the downside is that when people get that and they see that Royal Mail brand, that brand counts for something," he said. "That whole idea that in actual fact there is this local look, somehow gives that mail that kind of credibility."
Mike Haley, director of the National Fraud Authority, which is working with Royal Mail to tackle the issue, said more needs to be done.
"We're trying to make Spring Global and Royal Mail more aware of the human tragedy that this type of fraudulent mail impacts on victims. I think they need to understand the terrible consequences of delivery of this mail to some people."
Marilyn Baldwin, whose late mother Jessica Looke was scammed out of £50,000 after becoming addicted to scam mail, said in her mother's case, the Royal Mail stamp of approval was a factor in her belief that the scams were real.
"My mother used to say, it isn't a scam, it's genuine. This is the Queen's mail."
She said Royal Mail has a responsibility to society's most vulnerable.
"The Royal Mail are delivering, in effect, coach loads of criminals to the houses of elderly and vulnerable people. They are the link between the victim and the scammer."
In a statement, Royal Mail said it was working closely with police to stop scam mail from entering the system: "We very much understand the upset and disquiet that scam mail can cause households across the country, including vulnerable people.
"We do not want our postmen or women handling or delivering mail that causes harm. We have made significant progress in our efforts to root out scam mail as we intensify our drive against it."
Royal Mail said it has acted on complaints to halt distribution of some scam mail and is following up other leads to put a stop to even more.
Tom Heap turned his family's junk mail into a briquette for the fireplace
"If this turns out to be scam mail harmful to the recipients, we will stop it, irrespective of the cost and loss of revenue to Royal Mail," the statement said.
Spring Global said it too is working closely with police and other agencies to prevent scam mail slipping through. Of the "local look" postmarks, it said in a statement: "Local look is a recognised international marketing activity to prepare mail with a foreign postal indicia. This happens across the world and not just in the UK. The vast majority of companies using such a service are legitimate businesses that are looking to reduce costs and improve response rates."
Since January, Spring Global said it has worked with the Metropolitan Police and Royal Mail to get an estimated 6m items of scam mail out of the system.
Legitimate junk mail - or advertising mail - is, according to Richard Hooper, who authored
a report for the government on Royal Mail's future,
central to the financial viability of Royal Mail.
Mr Hooper found that income from legitimate advertising mail accounts for nearly a quarter of Royal Mail's letters business - £1.3bn out of a total of £5.4bn.
"The supreme irony is that without advertising mail, you would not have a universal postal service," he said.
Local councils are facing the cost of getting rid of the 1.7bn pieces of advertising mail which come through our letterboxes each year.
In Cornwall alone, the local council estimates that 4,000 tonnes of junk mail from various sources are ending up in landfill every year - enough to fill about 500 dustcarts that amount to about 3% of the overall waste Cornwall dumps into landfill.
Esther O'Bearagh, from Cornwall council, said it costs around £700,000 to landfill junk mail each year.
"It's quite incredible when you start doing the maths," she said.
Even if all that junk mail were successfully diverted to the recycling box, the cost to the county would sill be close to £500,000 a year at around £119 a tonne.
And it is a scenario that is believed to be replicated across the UK.
The Direct Marketing Association defended the junk mail onslaught, pointing out that sales due to junk mail amount to £16bn a year.
Executive Director Chris Combemale said more than half of the UK population made a purchase as a result of a piece of direct mail last year.
"I don't really like the phrase junk. Junk is untargeted, unuseful, unvaluable."
Royal Mail said junk mail accounts for 0.4% of average household waste in the UK.
Panorama: Why Hate Junk Mail? BBC One, Monday, 4 July at 2030 BST and then available in the UK on the