The priceless art collection of Britain's first prime minister, sold to Russia more than 200 years ago, is to make a triumphant return to its original Norfolk home.

Houghton Hall, near Fakenham, is to hold a five-month exhibition of some 100 paintings once owned by Sir Robert Walpole in a collection which has been regarded as one of the finest in the world.

Walpole had agents working all over Europe buying artwork which he had heard about.

His collection included work from Rubens, Sir Anthony Van Dyck, Velazquez and Rembrandt.

The paintings were displayed at his homes in Downing Street and Houghton Hall, which was built for Walpole between 1722 and 1735 and is now considered one of the finest Palladian houses in England.

At the time of Walpole's death in 1745, when the Downing Street paintings had joined the rest of the artwork at Houghton, the entire set was regarded as one of the world's finest art collections.

But Walpole's extravagance left his estate saddled with debt and this was compounded by the antics of his grandson, the 3rd Earl of Orford, who gambled away much of his inheritance and even reportedly lost in a bet the flights of stone steps which originally graced the east and west fronts of Houghton Hall.

More than 200 of the most valuable works needed to be sold to help save Houghton Hall and keep it in the Walpole family.

Although they were originally due to be sold at auction, Catherine the Great, Empress of Russia, offered to buy the lot for her Hermitage at the Winter Palace in St Petersburg.

In 1779 the Walpoles accepted £40,550 for the 204 works, equivalent to around £50m today.

The collection to this day remains one of the greatest treasures of the Hermitage Museum.

Although the heart of the collection remains, some of it has left the Hermitage over the years. Some paintings were sold by Nicholas I in the 19th century and others were reportedly raided and sold by Stalin.

There are stories of curators playing down some of the paintings' values to protect them from the dictator.

The return of the Walpole collection to Houghton Hall for the exhibition, which starts in May, is attracting interest from art-lovers across the world.

The principal rooms of the house will be restored to their exact appearance of the early 1740s, a time when Walpole was at the height of his powers, to provide an authentic backdrop.

Exhibition curator Dr Thierry Morel said: 'Sir Robert had an eclectic but very good taste in art. He bought the best of the best that was available at the time in Europe. He had agents all over the continent buying works that he had heard of. He also sent his sons to Italy and they brought back many masterpieces too.'

He added: 'I realised the Walpole collection was perhaps the most important collection of works coming from one country to Russia in the 18th century. I had been to Houghton many years ago and thought it was one of the most beautiful houses in Britain.

'I put two and two together and thought as the house was intact as it was in the 18th century and the pictures are mostly still in the Hermitage, why not reunite the house with the pictures?'

The return of the artwork has been a long-held ambition for the Marquess of Cholmondeley, Houghton Hall's current owner, who is a direct descendant of Walople through marriage.

When Lord Cholmondeley took over Houghton Hall more than 20 years ago, he made an extraordinary discovery.

He said: 'One of the first things I did was look through Sir Robert Walpole's desk in the library and I came across his original plans for the picture hang in three rooms. It was an extraordinary thing. I don't think my grandmother knew they were there and I'd certainly never seen them.'

Lord Cholmondeley said a visit to the exhibition, called Houghton Revisited, will bring so much exciting history to life. He said: 'There are many, many great characters involved and that will spark the imaginations of everyone – particularly the children who visit – and I am very keen to attract all ages to come and see it.'

The logistics of staging the exhibition are huge.

Each painting will be packed in a special wooden crate to travel to Norfolk from Russia by plane or ship. They will be left in the Stone Hall to acclimatise for at least 24 hours before being unpacked. Tickets to the exhibition are already on sale and there has been lots of interest from across the UK and beyond.

Dr Morel said: 'This exhibition is a dream come true for me. I hope all the visitors will share that excitement. I am pretty confident they will.'

The exhibition will run from May 17 until September 29.

For more information and to book tickets, go to www.houghtonhall.com/houghtonrevisited or call 01603 598640.

The collection is expected to be returned to The Hermitage Museum after the exhibition.