Have you been on a protest recently? Have you attended a political meeting, or stopped by at a rally? Were you stopped and searched, or photographed by police?

Even if you have done nothing unlawful, there is a possibility police have listed you on a database of so-called “domestic extremists”.

All that is needed to find out what information is being held about you in police intelligence files is to follow our step-by-step guide and send this simple letter. This is through a relatively powerful piece of legislation, the Data Protection Act.

Any member of the public can submit a request under this act asking for copies of the entries stored about themselves on the police’s databases of political activists. The act gives the public the right to see personal data held on them by police forces, and any other state organisation such as local councils, schools and Whitehall departments.

The Guardian is continuing to investigate the surveillance of political activists, ranging from the use of undercover officers to infiltrate the ranks of campaigners to attempts to recruit informers.

We have revealed how police have been secretly maintaining huge databases on thousands of political activists and campaign groups across the country.

We now want to delve further into these clandestine databases and hope that, if people find out what data is being stored on them, we can learn more.

Crucially, there are precedents. John and Linda Catt, an elderly artist and his daughter, received files showing how police had covertly recorded their presence at more than 80 demonstrations over four years, logging details such as their appearance and slogans on their T-shirts.

Even John Catt’s artistic endeavours were being recorded by police. “John Catt sat on a folding chair by the southern most gate of EDO MBM and appeared to be sketching,” one entry stated. “He was using his drawing pad to sketch a picture of the protest and police presence,” said another.

Another individual, Matt Salusbury, submitted a data protection request to Scotland Yard and discovered that police had photographed him coming out of an openly advertised public demonstration and had too recorded what he had been wearing and said at protests.

One entry showed that noted that at a demonstration against Britain’s biggest arms fair in 2007, police had noted that “at 1240 hours, Matt Salusbury, male IC1, observed cycling along Victoria Dock Yard wearing a high-visibility vest, black and red rucksack ... the bicycle he rode was a green Giant mountain bike with a carrier”.

He also obtained a photograph taken by police photographers of him when he went to an east London community centre for a public meeting to organise a concert to raise money for an anti-capitalist campaign. It shows how campaigners are also entitled to obtain photographs and video recordings of themselves which are held by police.

Your request needs to be directed to the Metropolitan Police, which took control of the main secret database of political activists run by the National Public Order Intelligence Unit (NPOIU).

The Metropolitan police has an online form for data protection requests. We have also formulated a sample letter as well. It is probably wise to fill out the form, attach your letter and send them off together (otherwise the Met may delay responding to your request for silly bureaucratic reasons).

The four-step process should not take more than 10 minutes, but you need to make sure you have supplied all the information that is required.

Step 1 Fill in the online form or use our sample letter to request your data. Be sure to request information from all three databases: the National Public Order Intelligence Unit; the CO11 Public Order Intelligence Unit; and CRIMINT.

Step 2 Proof of identity

The Met is entitled to ensure that you are who you claim to be, so you will need to provide evidence of your identity and address by supplying two different official documents which “provide sufficient information to prove your name, date of birth, current address and signature.”

For example, this would be a combination of driving licence, medical card, birth/adoption certificate, passport, utility bill or bank statement. These need to be recent.

Step 3 Pay £10

The Met can only charge a maximum of £10 for complying with your request. The force accepts cheques, British postal orders and international bankers drafts made payable to The Metropolitan Police Authority. You need to write your name, date of birth and address on the back of the payment in block capitals.

Step 4 Save a copy and Send

If you decide to use the sample letter, you need to send it to the Met’s data protection officers at: MPS Public Access Office, PO Box 57192, London, SW6 1SF.

Keep a photocopy of your request - they have been known to “go missing” or are “not received” by organisations. If you do not receive confirmation that the data protection officer has received your request within two weeks, ring the Met on 020 7161 3500 and ask to speak to the data protection unit, or email them – publicAccessOffice@met.police.uk. You are entitled under the act to get an answer within 40 days.

Know Your Rights

Don’t forget that you do not need to explain why you want the information or what you are planning to do with it. Remember that you can also get copies of videos and photographs of yourself under the act – for instance, those taken by CCTV cameras or forward intelligence teams. It is essential to specify the time and place when you think you were photographed.

Public organisations are allowed to withhold documents, or parts of documents, under various exemptions (for instance if the information would infringe the privacy of another individual, would help criminals or damage national security).

Appealing

The Met must explain clearly why information is being withheld, so you can challenge any denial of information by lodging an appeal, and asking the department to reconsider the decision.

If you do this, don’t forget the Met has previously released information on all the listed databases when requests have been received activists using this legislation. So precedent is on your side.

If you are unhappy with the Met’s response, you can also ask the information commissioner to investigate whether the organisation has acted correctly.

Send any complaint to the Information Commissioner at Wycliffe House, Water Lane, Wilmslow, Cheshire SK9 5AF; Tel - 01625 545 700.

The commissioner has the power to issue an enforcement notice compelling disclosure of the records, although the commissioner is most likely to try resolving the matter informally. You can also start legal action through the courts.

Help the Guardian?

Can you help us? We want to build on what we already know about these protest databases. The data that you obtain belongs to you, and there is no obligation to pass it onto any third party.

But if you are willing to help us find out more, then we would be grateful if you could get in touch. You can contact us discreetly; we will not reveal any of your details without your permission. We will guarantee your privacy and handle any information you pass to us with care.

rob.evans@theguardian.com paul.lewis@theguardian.com 0203 353 2000

Your address

Dear Sir/Madam,

I am writing to request all the information to which I am entitled to under section 7 of the Data Protection Act 1998 (a subject access request).

I am requesting a complete copy of all the information which is held about me on the databases controlled by the National Police Order Intelligence Unit; the CO11 Public Order Intelligence Unit; and CRIMINT.

I request that you disclose all comments, reports, emails, notes and any other written or other material from each of these three databases, as well as photographs or video footage of myself.

I am also requesting copies of any information about me that is being held by the National Public Order Intelligence Unit or the CO11 Public Order and Operational Support unit separately from these databases.

I wish to draw your attention to the fact that information held by these units and databases has previously been released under the Act.

I enclose a photocopy of [proof of your address, such as gas/electricity/telephone bill] as confirmation of the above being my home address. I have also enclosed a photocopy of my passport [or similar, such as driving licence] and a recent photograph of myself to aid your identification.

I understand that under the act, I should be entitled to a response within 40 days. I would be grateful if you could confirm in writing that you have received this request. I look forward to hearing from you in the near future.

Yours,