No, you cannot legally smoke weed in London. Cannabis is a Class B controlled drug across the whole of the United Kingdom, and there is no local exception for London, no allowance for personal use, and no minimum quantity that police will ignore. Get caught and the outcome ranges from an on-the-spot warning to years in prison, depending on how much you have and what you were doing with it.1GOV.UK. Drugs Penalties
Why It’s Illegal Everywhere in the UK
Cannabis sits in Class B under the Misuse of Drugs Act 1971, alongside amphetamines and ketamine.2Home Office. Drug Licensing Factsheet: Cannabis, CBD and Other Cannabinoids The law covers every form of the plant: dried flower, resin, edibles, oils, vape cartridges, concentrates. Possessing any of them without a valid prescription or Home Office licence is a criminal offence, whether you are a UK resident or a tourist here for the weekend.1GOV.UK. Drugs Penalties
What Happens If Police Catch You
Simple possession carries a maximum sentence of five years in prison, an unlimited fine, or both.1GOV.UK. Drugs Penalties The maximum is rarely the reality for a small amount, but the range of outcomes still bites.
Officers on the street usually have three options:
- A cannabis warning, available for a first offence with a small amount clearly for personal use. You must be an adult with no prior warnings, no convictions, and no aggravating factors. It is not a criminal conviction, but it goes on the Police National Computer and shapes how officers deal with you next time.
- A Penalty Notice for Disorder, a £90 fixed fine typically used for a second minor offence. Paying promptly avoids a criminal conviction, though the record can appear on enhanced background checks used in sectors like education and healthcare.3GOV.UK. Penalty Notices for Disorder Guidance
- Arrest and prosecution, used for larger quantities, any hint of dealing, or repeat offences. This is the route that leaves you with a criminal record affecting employment, housing, and travel.
Supply and production are treated far more seriously. Selling, sharing, or growing cannabis, including a couple of plants on a windowsill, carries up to 14 years in prison and an unlimited fine.1GOV.UK. Drugs Penalties Prosecutors do not need to prove an actual sale to charge intent to supply; they infer it from quantity and surrounding evidence.
Smoking in Public Versus at Home
Legally there is no difference. Smoking a joint in Hyde Park and smoking one in your flat are both criminal offences with the same maximum penalties. What differs is how likely you are to get caught.
Public use draws police attention quickly. The smell alone gives officers reasonable grounds to stop and search, and London’s density and CCTV coverage make casual outdoor smoking riskier than most people assume. Streets, parks, and public transport are where warnings and fines most commonly happen.
At home the odds shift but do not disappear. Neighbours report the smell. Most tenancy agreements in England prohibit illegal activity on the premises, so a landlord who finds evidence of cannabis use can begin eviction proceedings, and repeated complaints can pull in police and council anti-social behaviour teams.
Driving After Smoking
Drug driving is a separate offence with its own penalties. The legal blood-THC limit in England and Wales is 2 micrograms per litre, set close to zero to reflect a zero-tolerance approach to illegal drugs behind the wheel.4GOV.UK. Changes to Drug Driving Law Cannabis stays detectable long after the high wears off, so smoking in the evening and driving the next morning can still put you over.
A conviction brings:
- A minimum one-year driving ban
- Up to six months in prison
- An unlimited fine
- A criminal record that stays on your driving licence for 11 years
If drug-impaired driving causes a death, the maximum penalty rises to life imprisonment.5GOV.UK. Drugs and Driving: The Law London police use roadside saliva tests that detect cannabis, and refusing the test is itself an offence.
What About Medical Cannabis and CBD
Medical cannabis has been legal in the UK since November 2018, but access is narrow.6GOV.UK. Rescheduling of Cannabis-Based Products for Medicinal Use in Humans The NHS prescribes it only for a handful of severe conditions where other treatments have failed, and GPs cannot write those prescriptions. Most patients who use medical cannabis in the UK do so through private clinics and pay out of pocket. Possessing cannabis without a valid UK prescription is still a criminal offence, including medical-grade products bought elsewhere.7NHS. Medical Cannabis (and Cannabis Oils) A US state medical marijuana card carries no weight here; travellers already prescribed cannabis abroad need proper documentation and should check with the Home Office’s Drug and Firearms Licensing Unit before flying in.8GOV.UK. Take Medicine In or Out of the UK
CBD is where people trip up. Pure CBD is not controlled, but products containing THC or other controlled cannabinoids must qualify as an “exempt product” under the Misuse of Drugs Regulations 2001 to be legally sold; anything that doesn’t qualify is treated as a controlled drug. CBD food products also need Food Standards Agency authorisation as novel foods, and many products sold in London shops have not completed that process.9Food Standards Agency. Cannabidiol (CBD) Guidance Raw CBD flower or “hemp flower” is the biggest trap. Even if the THC content is negligible, the flower comes from the cannabis plant and is controlled under the Misuse of Drugs Act. Buying, possessing, or selling it carries the same legal risk as any other form of cannabis, whatever the packaging claims.
Extra Risks If You’re Visiting
A cannabis offence in London can outlast the fine or warning by years if you are not a UK resident. The Home Office must refuse entry or cancel a visa for anyone convicted of an offence resulting in a custodial sentence of 12 months or more, and persistent offending or conduct showing “particular disregard for the law” can trigger refusal on its own. Short-stay visitors face a lower threshold: any custodial sentence can result in refusal unless more than 12 months have passed since it ended.10GOV.UK. Suitability: Grounds for Refusal / Cancellation – Criminality
The problem can also follow you home. The US Embassy in London advises that anyone ever arrested, cautioned, or convicted of any offence should apply for a full US visa rather than travelling under the ESTA programme.11US Embassy London. Ineligibilities and Waivers A UK cannabis caution does not automatically bar you from the United States, but trying to enter without disclosing it can lead to being turned away at the border, or a permanent finding of inadmissibility for misrepresentation.