Not all of the portraits are exceptional artistically, although there are self-portraits by William Hogarth, Sir Joshua Reynolds and other British artists of note. Some, such as the group portrait of the participants in the Somerset House Conference of 1604, are important historical documents in their own right. Often, the curiosity value is greater than the artistic worth of a work, as in the case of the anamorphic portrait of Edward VI by William Scrots, Patrick Branwell Brontë's painting of his sisters Charlotte, Emily and Anne, or a sculpture of Queen Victoria and Prince Albert in medieval costume. Portraits of living figures were allowed from 1969. In addition to its permanent galleries of historical portraits, the National Portrait Gallery exhibits a rapidly changing selection of contemporary work, stages exhibitions of portrait art by individual artists and hosts the annual BP Portrait Prize competition.
The collections of the National Portrait Gallery were stored at Mentmore Towers in Buckinghamshire during the Second World War, along with pieces from the Royal Collection and paintings from Speaker's House in the Palace of Westminster.