Dawn raids by the Serious Fraud Office have led to four arrests in an investigation into a £140m property investment scheme.

SFO director Nick Ephgrave, in his first public speech earlier this month, stated that the SFO has 'already gone through more front doors in the last three months than in the last three years'.

He added: ‘This provides momentum to the investigation, it gets people in an interview room, you look them in the eye and start asking questions, put them under some pressure, search the house, crack the evidence.’

This week the SFO raided three residences in Merseyside and Greater Manchester and made four arrests in connection with alleged fraud.

The raids, which were supported by the National Crime Agency, coincide with the SFO’s announcement of its criminal investigation into international property investment scheme Signature Group.

Signature Group, which operated for more than seven years, bought predominantly historic buildings within the UK for redevelopment into luxury hotels, residential apartments and office spaces. The business’ portfolio included Millennium House in Liverpool, the Coal Exchange in Cardiff, and a cruise liner marketed as a ‘flotel’ to be moored off Canary Wharf, London and sail to Ibiza.

The SFO said investors loaned money to Signature or purchased a hotel room, apartment, or office space in one of the group’s properties, with promised returns on their investment of between 8% and 15%. The business went into administration with losses of up to £140m, involving 1,000 investors from around the world.

Ephgrave, who joined the SFO in September last year, said: ‘The scheme offered attractive returns and used much-loved local landmarks to lure investors. We have people up and down the country left out of pocket, and buildings left derelict at the centre of our cities.

‘Today’s arrests and searches will help us reconstruct exactly what happened. This is now an active criminal investigation.’