Allen was Nelson's devoted but occasionally difficult manservant, whose greatest regret was that he was not on board 'Victory' at Trafalgar and so not present at Nelson's death. Sir Richard Keats, when Governor of Greenwich Hospital, admitted him as a Pensioner in October 1831 on the request of Sir Thomas Hardy, then at the Admiralty, even though he was not technically a seaman. Hardy (Keats's successor as Governor) put up the monument on Allen's grave which can still be seen in the former Hospital burial ground (now the grounds of Devonport House) to the west of the NMM buildings. Allen's age is consistently overstated in references related to his admission to Greenwich Hospital, which gives it as 66 or 67. He appears to have been baptized at Sculthorpe, Norfolk, on 23 December 1771, suggesting he was in fact only 59 when admitted. From around 1817 Allen had been a servant of Nelson's brother-in-law, William Bolton, on whose death in 1830 he faced hardship until a Norfolk gentleman and ex-naval surgeon, Page Nichol Scott, gained support for his admission to Greenwich.

Scott is said to have had a memorial card made after Allen's death to raise funds for his widow: see Appendix to the 1840 edition of Clarke and Macarthur's 'Life of Nelson' and Lt G.S. Parsons 'Nelsonian Reminiscences' (1843 ed). What that was remains to be confirmed. This woodcut may be the same image but is now known to have appeared illustrating a two-side sketch of Allen's life in 'The Mirror' , (pp. 305-06): the detached page seen gives no date, which remains to be confirmed. There is also a drawing of Allen by Daniel Orme in the collection (PAG6838) and an oil portrait sketch of him by John Burnet (BHC2510). The latter is a study for his 'Greenwich Pensioners celebrating the Battle of Trafalgar' (Apsley House). In this, the related print and the watercolour copy by S. P. Denning (NMM) from which Burnet engraved the plate, he is shown holding a portrait of Nelson in the group on the left.See also PAD4247, another copy of the featured print.