Alpha and Green Park-branded companies sold investments in leasehold units between 2014 and 2019, promising investors 8-10% returns on their investment over the first 10 years.

The SFO suspects the Alpha-branded companies of fraudulently misleading investors into purchasing leaseholds for student accommodation in Leicestershire, Lancashire, Staffordshire and West Yorkshire.

Green Park-branded companies are also suspected to be part of a similar scheme, selling leaseholds for holiday homes in Devon.

Over 1,500 investors from around 50 different countries invested an estimated £150m into the leasehold schemes on the back of these guaranteed returns, but all stopped receiving returns in 2018.

Yesterday the SFO carried out a series of coordinated dawn raids, interviews and mandatory requests for evidence across the country, following a six month covert investigation into the Alpha and Green Park businesses.

Working with Cleveland Police, the SFO carried out formal searches on multiple properties, arresting and interviewing one suspect. At the same time, the SFO also issued several Section 2 notices, which force companies to provide relevant information.

The directors of the companies are thought to have made around £20m from the schemes.

Mick Gallagher, chief investigator at the Serious Fraud Office, said: “Thousands of ordinary people lose their pensions or life savings on risky schemes, while those at the top line their own pockets and enjoy a lavish lifestyle. The Serious Fraud Office is committed to delivering justice for victims of fraud and corruption. We invite anyone who believes they have a connection with our investigation to come forward.”

Investigators will contact UK-based investors and ask them to fill out a questionnaire by 30 November.