Robert Holt Carpenter was born in England probably in 1819 or 1820, the son of a cabinet-maker, Edward Carpenter, and his wife, Louisa A'Mutie. He trained as a bookbinder, probably in London, and by subsequent repute participated in the 1839 Chartist demonstrations. On 18 September 1841 at Bath he married Harriet Pricture, a domestic servant; they sailed for New Zealand on the Birman, arriving in Wellington in March 1842. Their only child, Ellen Louisa, was born in July; shortly afterwards they tried moving to Nelson, but the ship was wrecked and they lost most of their possessions. In later years Carpenter would speak with great feeling of the hardships endured by working class immigrants. The family returned to Wellington, where Carpenter applied unsuccessfully in October 1842 for the post of messenger to the borough council, and took up his trade of bookbinding, for which demand was then limited.
Originally he worked through the Wellington Independent newspaper office, but by 1850 he was in business on his own account. He was now consolidating a local reputation for eccentricity and political independence, and had developed his enduring opposition to Isaac Featherston. The establishment of the Wellington Settlers' Constitutional Association in late 1848 found him in a small group of its vocal opponents, with such men as Robert Stokes, the Tory editor of the New Zealand Spectator and Cook's Strait Guardian, and Governor George Grey's nominee councillors. When brought to public prominence in the agitation of 1850 and 1851, he was described as 'the Wellington Quilp', with reminders of his past as 'an armed Chartist'.
When the first provincial council elections were held in 1853, Carpenter supported R. J. Duncan, a well-known advocate of cheap land, and then, as an afterthought, stood himself, coming 15th of the 16 candidates. He was elected when the council was enlarged in 1856, and re-elected in November 1857 with Edward Jerningham Wakefield's radical reform group, ardently opposed to Featherston. Each time, Carpenter was nominated by men with a householder qualification – small tradesmen not otherwise active in public life. Carpenter represented and always spoke for this section of the community. In 1861 he lost his seat, with other members of Wakefield's party, but returned in February 1864 in a by-election. He again lost his seat in the election of April 1865, one of a small group of candidates openly opposing the popular Featherston.
His career in provincial politics was chiefly notable for frequent motions calling for returns of expenditure, although he also moved that the council should subscribe to the Wellington newspapers, thereby contributing to the foundation of a national newspaper collection. He opposed William Fox's endeavour to introduce the secret ballot for elections, departing from the original Chartist demands, although he continued to advocate other Chartist principles. His one continuing policy was opposition to Featherston.
After 1865 he remained out of provincial politics. In 1868 he was returned unopposed to represent Thorndon Ward on the Wellington Town Board, apparently in response to John Plimmer's comment at the ratepayers' annual meeting that 'he was always finding fault, but had no remedy to offer. [He] ought really to take his seat at the Board.' On the town board his contribution was limited: he opposed the application of the Municipal Corporations Act 1867 to Wellington, and spoke for the principle that rates should be as low as possible and should be spent in the ward in which they were raised. In 1870 the town board became the city council and board members became councillors. In 1871 Carpenter was defeated by the wealthy merchant William McLeod Bannatyne, and he retreated into private commercial life.
Carpenter had established himself as a bookseller early in the 1850s, trading chiefly in second-hand but also in new books. He apparently read his own stock extensively, drawing on his reading to illustrate political speeches and, no doubt, everyday conversation.
This continual display of erudition would have contributed to his reputation for eccentricity, as would his notable absence from virtually all charitable subscription lists. Harriet Carpenter supplemented their income by making fancy waistcoats, and his business prospered sufficiently to let him invest on a small scale in rural land. By his retirement, forced by paralysis in the mid 1880s, he was a confirmed local identity, whose Molesworth Street shop contained an extraordinary collection of old books, many worthless but some rare and valuable, many of which he would refuse to sell. He died on 24 February 1891 at Wellington.
Harriet Carpenter lived until 1903. Ellen married Frederick Cooper, founder in 1860 of the firm of seed merchants, F. Cooper Limited.