The Tate gallery has bought three British masterpieces - one a Constable - with help from the Heritage Lottery Fund.

John Constable's Suffolk landscape Fen Lane, East Bergholt, is said to mark a turning point in the painter's career.

The collection has also secured Johan Zoffany's two portraits of the children of the 3rd Earl of Bute.

Tate director Sir Nicholas Serota described the works as "exemplary paintings by two of the most significant figures in British art".

The Zoffany paintings are a rare pair of companion portraits

"We are thrilled by these acquisitions which will allow us to present these artists in even greater strength," he added.

The National Art Collections Fund and members of the Tate gallery also contributed to the purchases.

The Constable painting was bought from a private collection for an undisclosed sum - believed to be nearly �3m.

The work had been on loan to Tate Britain, but was seen as at risk of auction and export.

'Highly innovative'

It belongs to a group of mid-sized canvasses that Constable painted in Suffolk in the open air during the period 1814-17, and depicts a lane which Constable used to use when walking to school in Dedham as a boy.

A Tate spokeswoman said: "Constable's open-air practice of this time was highly innovative and ultimately had an important influence on the developments in landscape painting which led to impressionism."

The two Zoffany portraits - Three Sons of John, 3rd Earl of Bute and Three Daughters of John, 3rd Earl of Bute - were painted around 1763-4.

They are rare, being one of very few pairs of pendant, or companion, portraits to have remained together in the same collection.

The National Art Collections Fund contributed a total of more than �500,000 to the Tate purchases.