A secret £2 million fortune left by tragic screen siren Diana Dors could be uncovered almost 20 years after her death, thanks to expert Sussex codebreakers.

Before the actress died in 1982, she handed her eldest son, Mark Dawson, a scrap of paper covered in more than 300 seemingly random pencilled-in letters.

She told him that cracking the code would reveal where her £2 million fortune was stashed away.

She also said her husband, the actor Alan Lake, had the password which would unravel the code as well as the explanations for what the message meant.

However, just five months after Dors' death from cancer in May 1982, her grief-stricken husband shot himself without passing on the code's secrets.

Mr Dawson, 43, struggled for almost two decades to make sense of the message but failed.

He only made progress when he turned to Horley-based computer forensics and cryptography firm Inforenz, set up two years ago by Patcham resident Andy Clark.

The firm's experts usually have to recover data from IT systems but instead spent two days trying to crack the handwritten code using mere brainpower, rather than their super-computer Deep Thought.

Chief cryptographer Vince Gallo said: "Our first task was to establish what encryption technique had been used.

"Because personal computers were not available when Diana Dors created her document, we needed to adopt a pre-PC mindset. She was likely to have used a classic encryption technique."

The firm eventually realised she had used something called the Vigenere cipher.

This was developed in the 16th Century by French diplomat Blaise de Vigenere and was used by the Vatican for secret diplomatic communications.

It was not cracked until 1863, when a Prussian military officer devised a statistical method for breaking it.

The code is now taught as a standard part of training for cryptography students.

Mr Clark said: "It was not a complex cipher to solve. The challenge we faced was working out what sort of cipher it was in the first place.

"It was a very emotional moment when Mark actually saw the code revealed. We hugged and he was shaking."

Mr Dawson, who lives in California, said: "Inforenz did the impossible. In discovering the code was Vigenere and in cracking it, they succeeded where others had failed over 21 years.

"If it was not for their skill, wisdom and expertise, I would have taken the uncracked code to my grave."

The message was revealed as a list of places such as Brighton, Leeds and Birmingham, with names written next to them.

Mr Clark said: "Our suspicion at the moment is that these refer to names and pseudonyms Diana Dors used to manage her bank accounts and where."

Next to the word Brighton was listed the word Pyewacket.

Mr Clark said: "That's a very unusual word and Mr Dawson is hoping that people like bank managers or tellers who dealt with Diana Dors will come forward and shed light on what it means."

Although the fortune still remains out of reach, Mr Clark believes Mr Dawson has taken a crucial step in his investigations.

He said: "On the assumption that banks look after money well, then it should still be out there somewhere.

"There is £2 million plus interest up for grabs somewhere, so I'd say it's worth Mr Dawson persevering. We think people who can help will be sympathetic.

"I expect the Inland Revenue would be interested too. Perhaps they will even be of some help to him."

Miss Dors used to live at Palmers Farm, Billingshurst, and regularly visited Sussex after moving to California and then Berkshire. She died in Windsor at the age of 52.