Boris Johnson has this week been plotting his first 100 days in office in a £9.5m residential Westminster townhouse owned by the senior Sky television executive Andrew Griffith, who rose to the top of the broadcaster during its Murdoch years.

Johnson has been holed up for at least four days in Griffith’s Grade II-listed, five-storey house planning his transition to government, with visitors including senior Tories Jacob Rees-Mogg, Stephen Barclay, Matt Hancock and Gavin Williamson.

Griffith, who is Sky’s chief financial officer and chief operating officer, is understood to have offered Johnson the use of the house in a personal capacity. He is a former Conservative party candidate who was appointed to the board at Sky in 2008 when Rupert Murdoch’s News Corp owned 39% of the company, then working under James Murdoch as chairman.

Murdoch’s 21st Century Fox lost a bidding war for Sky last year and James Murdoch, its on-and-off-chairman, relinquished the position for good in November, but Griffith stayed on at the company alongside its chief executive.

Johnson, who is expected to enter No 10 next week, has been spending up to 13 hours a day at Griffith’s lavish townhouse in recent days, with sources on his team saying he has switched his focus towards strategy for government.

His “transition” team is headed up by Hancock, alongside fellow Tory MPs Oliver Dowden and Rishi Sunak, while Steve Baker, a leading Eurosceptic, is also understood to be “feeding in” to the plan for the first 100 days.

A Johnson campaign source said Griffith had kindly opened up his home to let members of the transition team meet there, but the businessman was not part of that operation. Sky said it was “a personal matter”.

Johnson’s campaign is officially based at a £3m townhouse on Lord North Street in Westminster from which Iain Duncan Smith masterminded his leadership victory in 2001. This is owned by Greville Howard, a multi-millionaire Eurosceptic businessman.

Johnson has hugely outgunned his rivals in terms of donations during the contest, receiving more than £500,000 since May.

With the threat of an election potentially looming, Conservative party headquarters is hoping that Johnson as prime minister will be able to pull back donations that had somewhat dried up under Theresa May.

Johnson’s haul included a donation of £100,000 from the strongly pro-Brexit venture capitalist Jon Moynihan, who played a leading role in the finances of the official Vote Leave campaign.

Johnson also received a combined £28,000 from digger company JCB and its Brexit-supporting chairman, Anthony Bamford. So far this year, Johnson has received nine separate donations from JCB or Bamford.

Donors to the Johnson camp also included Rosemary Saïd, the wife of billionaire philanthropist and arms deal fixer Wafic Saïd, as well as a combined £20,000 from the investment firm Killik and Co, its founder and his wife.

Under Conservative party rules, there is a maximum permitted spend on a leadership campaign of £135,000 per candidate. However, some of these donations can be spent on other aspects of an MPs’ work.

In previous Tory leadership elections, some candidates have given any excess once the race was over to Conservative campaign headquarters for the party to use.