"We have attracted good people and done the right cases," says Serious Fraud Office (SFO) director David Green as he prepares to step down from his role after six years with the organisation.

 "We have gone back to what the organisation was always meant to be: an investigator and prosecutor tackling the most serious fraud and commercial bribery."

When Green (pictured) took up the role of director in 2012, the SFO was widely considered to be in bad shape.

A £4.5m settlement in 2014 with property entrepreneurs Robert and Vincent Tchenguiz over dawn raids on their homes that had been criticised by the High Court in 2012, and the revelation that the agency paid out almost £1m in exit payments to staff without approval had come in quick succession, with the blows leading to the organisation being dubbed the "Serious Farce Office" by some.

As Home Secretary, Theresa May was keen to abolish the SFO and hand its responsibilities over to the National Crime Agency, and the idea was still in contention as recently as last year, until she failed to secure a parliamentary majority in the general election.

Sitting in his office in the SFO's home in the Canadian High Commission, overlooking Trafalgar Square, Green – who steps down from the agency in April – admits that during that period the agency "wasn't in a good place", adding: "But that is history now."

"Before I came, there was a perception that the SFO wasn't up for a fight, wasn't interested in prosecuting and was keener on making deals. I think we banished that perception fairly swiftly," Green says. "I set myself the task when I started of wanting to restore the SFO's sense of corporate self-respect and bring it to the top of its game as a crime fighting institution," he adds.

I shall hawk myself around the bazaars of legal London and see if I can muster a flicker of interest

He says that as a result of these changes, the body is now "capable of attracting really good people" despite the difficulty of competing with ever-higher private sector remuneration. It is something that he is particularly proud of, with the number of lawyers in the SFO more than doubling during his tenure from 45 to 99, with the body also housing 31 accountants working in an investigatory capacity as well as 21 accredited financial investigators.

He is also proud of the way the agency has evolved to use new tools like deferred prosecution agreements (DPAs) to add additional bite to its investigatory powers.

He argues that is important that his successor keeps pushing the agreements, which allow companies to self-report and cooperate with the SFO in order to avoid the risk of costly trials and the potential damage of a conviction.

"When I became director, companies used to say we are not going to self-report to the SFO because it is too uncertain, we don't know what the outcome will be," says Green. "With DPAs there is an absolutely clear offer in place – if a company self-reports and is genuinely cooperative, then they stand a good chance of being invited into DPA discussions."

In a landmark case for the agency, the SFO and Rolls Royce entered into a DPA following a four-year investigation into false accounting and failure to prevent bribery. The DPA saw the motor company agree to pay out £497.25m last January – a fine that remains the largest ever settlement with a company in the UK for criminal conduct.

Green acknowledges that after the threats to the agency's existence, wins like this have helped significantly, adding that "the SFO is not designed to live on a diet of mortgage and boiler-room fraud – we are after the top-most tier of fraud and corruption".

Not that the SFO has been short of media scrutiny in the five years since he took on the job, but he says there's "no use whinging about occasional critical coverage".

What he admits is frustrating though is when the media reports "in total ignorance", describing cases as "failed" following an acquittal.

He also concedes it can be difficult to explain the difference in reach for prosecuting economic crime in the UK compared with the US.

"There is a comparison often made by the man in the street between how crimes by companies are dealt with in the US and the way they are dealt with here. In the US they have vicarious liability, so if someone commits a crime in the course of their employment the company is legally responsible.

"In the UK you have to identify the controlling mind in the company, usually at board level, and prove that they were complicit. One change that I have suggested might assist is to use the failure to prevent model, and expand that into an offence for a company failing to prevent acts of economic crime by people associated with it."

Eyebrows raised, Green acknowledges that it is "self-evident" that Parliament might be too busy with other matters for any reform to happen soon, raising the spectre of Brexit that is haunting the legal industry. The SFO has contributed to government consultations on European collaboration post-Brexit, with Green adding that "it is in everybody's interest that collaboration is preserved".

"There are institution within the EU such as Europol which are beneficial to us and there are mechanisms such as the European arrest warrant and European investigation orders which are extremely useful," he says. "After Brexit, this country is going to need inward capital investment and that is attracted by a level playing field for investors and by a rule of law jurisdiction.

"Those must be preserved and the SFO plays its part in ensuring a level playing field and in preserving the UK as a rule of law jurisdiction."

On the future of white-collar activity in the UK, Green says that he approves of plans for a new court complex in the City, adding that there is little not to like about the idea of a new commercial and financial court.

He is more coy about his own future though, sighing at the hint of a question about where he will go next. Despite ongoing rumours of moves to high-paying US firms, he insists that for now his plan is to take a few months off when he steps down in April, before making any decisions.

"After that," he concludes, "I shall hawk myself around the bazaars of legal London and see if I can muster a flicker of interest."