LONDON.- A rarely-seen portrait of the Duke of Wellington from a private collection and commissioned by one of his closest female friends is set to be a big draw at the National Portrait Gallery’s exhibition devoted to the Regency artist Sir Thomas Lawrence, which opens on Thursday 21 October. Apart from a two-month exhibition in Bristol in 1951, the portrait has never been seen in public. The portrait – which shows Wellington in civilian clothes rather than military attire – is widely held to be one of the artist’s most celebrated paintings. It is also one of the most successful and revealing portraits by any artist for whom the Duke sat. It comes as close as any to penetrating Wellington’s aura of heroism and capturing the essence of the man. Commissioned in 1820 by Wellington’s close friends the diplomat Charles Arbuthnot and his wife Harriet, whom he had met in Paris in 1814, the portrait was exhibited