This is why thousands of people were getting high in London's Hyde Park on Sunday

Today marks the the unofficial "cannabis day" across the world, also known as 4/20, where weed users try to push their respective governments to legalise the illegal substance.

However, because most people have to go to work on a Monday, in Britain, activists held a big rally in London's Hyde Park on Sunday where around 10,000 gathered to get stoned in the face of the police and their sniffer dogs (which must have been over-stimulated that day).

It led to 53 arrests for possession.

Pro-legalisation group Norml UK, which organised the gathering, said Britain is only one out of the 126 countries around the world that are holding similar events to try and get their governments to de-criminalise the possession and use of weed.

Activists point to the success of marijuana legalisation in Colorado in 2014. It created 10,000 jobs and sales brought in £29 million ($44 million) in taxes in the first year. However, the New York Times reported that marijuana tax revenue isn't going to bring in nearly as much money as we thought.

In Britain, economists have also also touted the legalisation of marijuana to be a potential boon. The Institute for Economic and Research said in report published in 2013 that the country could make up to £900 million a year through cannabis industry taxation.

Furthermore, crime rates also dropped within the first three months in the city of Denver, where overall crime dropped by 14.6%. Violent crime and assaults also feel by 2.4% and 3.7%, respectively.

So why hasn't Britain legalised the drug yet?

Activists believe that corporate lobbying and the potential decline in revenue for medical marijuana globally could be a big reason for the lack of movement on cannabis legalisation.

In the US, 23 states, most recently Georgia, and the District of Columbia legalised the use and production of medical marijuana, while in Britain, there is no such law.

"It's hard to say why the government hasn't legalised cannabis because modern government is incredibly secretive in nature and it's impossible to know who's being lobbied by who and for what reason," said Alex, 29, to Business Insider. Alex works in retail investment and attended the demonstration on Sunday in Hyde Park.

"Corruption and the vast profits made on the black market would be one suggestion. Another would be to protect revenue for pharmaceutical firms by essentially giving them a monopoly over a plant which belongs to nature. I also think there's a moral boundary which has been established by middle England which no politician dares to cross. The chattering classes love to look down on people and can't get enough of a good moral panic so they get plenty of opportunities for both from cannabis users."

Conflicting science reports

Scientific studies over the impact of long term marijuana use have also caused conflict over whether marijuana should be legalised.

Some studies, as highlighted in the Scientific American, showed that "cannabis might trigger psychosis in vulnerable individuals" but conflicting evidence show that there was no increase in schizophrenia among long term weed smokers.

"There are scientists on both sides of the debate and I know which ones I believe are giving an honest scientific account and which have an agenda they want to promote. I'll leave it to you to decide which scientists you want to give weight to," said Alex to Business Insider. "There is a definite skew in media coverage of cannabis just as there is with all coverage of any culture outside of the mainstream. Journalists don't want to find truth, they want to find the facts which fit their pre-determined editorial line. People want to read about low-life weed smokers, people trafficking and how awful anything outside of wholesome British culture is. The media is happy to oblige."

In terms of safety, a study in the journal Scientific Reports, showed that marijuana is about 114 times safer than alcohol, when scientists looked at the amount of the drug a user would normally consume and compared that to the amount of that substance that would kill the average person. Business Insider looked at the discrepancy between the laws on alcohol and marijuana are totally out of sync with the science here.

Activists point out that studies surrounding cannaboids, chemical components of cannabis, also are potentially beneficial in the treatment of cancer-related side effects.

What's next for Britain?

Although a number of Conservative back benchers and even the influential Tory think-tank Bright Blue urged David Cameron's party to ease the laws on marijuana legalisation, no major political party has mentioned the de-criminalisation of cannabis in their manifestos.

It is unlikely that they will either as taking a stance on the issue could cost them popularity in the polls which none can afford, considering how the Tories and Labour are currently ranked neck and neck. Only the Green Party, which is outlier for power, has called for the total legalisation of cannabis.