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Mr and Mrs Blair jointly hold title deeds to a £7.5 million Grade II listed townhouse close to Hyde Park, the £1.7 million mews house behind it, and an £8 million Grade I-listed 17th century manor house, formerly owned by Sir John Gielgud, near Aylesbury, Bucks.

Cherie and Euan, 31, own the £4.4 million Georgian townhouse in Marylebone, West London, where he lives with wife Suzanne.

Mrs Blair and her son also own 24 rented flats spread across properties in Stockport and Manchester, and purchased under the name Oldbury Residential Limited.

^{Euan Blair and his mother own 24 rented flats in Stockport and Manchester Picture: Geoff Pugh}

Aspiring football agent Nicky, 30, owns a £1.8 million four-storey townhouse in Marylebone, West London, while Kathryn’s name appears on the deeds to £1.2 million mews house which backs onto Euan’s home.

In August 2014, when the property is believed to have been owned by Cherie and Euan, Westminster Council granted permission to excavate a new basement level, enlarge the dwelling area, and create a courtyard enclosed by a 2m tall opaque glass screen.

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They approved a request to raise the height of the roof and parapet wall on the boundary with Euan’s main home one month later.

^{Kathryn Blair’s name appears on the deeds of a house worth £1.2 million Picture: Richard Young / Rex Features}

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Ownership of the Mews house appears to have been transferred to Kathryn Blair in January this year, according to the Land Register.

Adding the value of Mr Blair’s properties to the value of his companies, the money in his accounts and his earning from regular speaking engagements puts his overall wealth at more than £58 million.

Since 2008 the family may also have made gross profits of £1.6 million after selling three more London properties and former Sedgefield MP Mr Blair’s constituency home in County Durham.

The figure helps offset Mr and Mrs Blair’s far larger mortgages with Lloyds Bank and JP Morgan, for whom Mr Blair works as a £2 million per year adviser.

Mr Blair, who earns as much as £200,000 for a single speaking engagement, has previously insisted he is worth less than £20 million.

His profitmaking affairs are administered by Tony Blair Associates (TBA).

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TBA is the trading name for a network of companies, limited liability partnerships and limited partnerships, one half under the Windrush Ventures umbrella, and the other under the name Firerush Ventures.

Windrush is the channel for Mr Blair’s governmental advisory work, while Firerush is the business that offers consultancy services to firms and sovereign wealth funds.

They are listed at an address a stone’s throw from Whitehall and the Houses of Parliament and close to St James’s Park in the heart of Westminster.

Both are registered in England and Wales and pay full UK taxes. There is no suggestion of wrongdoing.

WVL alone is valued at more than £17 million, after multiplying its most recent profits by a factor of 13 – far lower than the average multiple of 18 used in the FTSE 250.

Last year the firm, which employs 37 staff, recorded an overall turnover of more than £14 million, including profits of £1.2 and more than £5 million in the bank, according to Companies House records.

The company also announced operating costs – including staff salaries, social security, travel and accommodation expenses, rent and other sundries – of £13 million, up from £12.1million in 2013.

In fact, over the last five years such expenditures have totalled £56 million.

FVL has reported more modest gains – from capital reserves of just £25,000 in 2010 to £680,000 last year, down from a 2013 peak of £1.6 million.