Protheroe’s father, the founder of an extensive industrial empire of collieries and iron works in the Forest of Dean, came from a prosperous family of bankers, West India merchants and local Whig politicians at Bristol, where he was Member, 1812-20. At the 1826 general election Protheroe offered for the open borough of Evesham as ‘a Whig’. After a token contest got up by the independents, who accused him of attempting to forge an ‘unnatural coalition’ with the sitting Tory, he was returned in second place.
Protheroe divided for the Wellington ministry’s concession of Catholic emancipation, 6, 30 Mar., and presented and endorsed petitions in its favour, 16 Mar. 1829. He secured returns of wills and administrations transmitted to the legacy office the following day. He was a regular speaker and presenter of petitions against proposals to relocate Smithfield cattle market, which he denounced as ‘absurd and ludicrous’, 14 May, and was a majority teller against the bill, 15 May. He welcomed the addition of a clause to the friendly societies bill prohibiting ‘compulsory payments for entertainment’ at meetings, 15 May. That day he endorsed the anatomy bill, explaining that the evidence taken before the committee had ‘completely removed’ his initial misgivings. He divided for allowing Daniel O’Connell to take his seat unimpaired, 18 May. He doubted that Buckingham House could ‘be completed for the estimate now framed’, 25 May, when he voted against the grant for the marble arch, but thought ‘no fraud could be fairly imputed’ to John Nash in his handling of crown leases, 19 June 1829. (He welcomed the report of the select committee vindicating Nash, 2 Mar. 1830.) He divided for Lord Blandford’s parliamentary reform scheme, 2 June 1829. On 4 Feb. 1830 Protheroe proposed an amendment to the address on the need to alleviate distress, arguing that ‘discontent from large masses’ and the ‘growing contempt in which the House is held’ could only be dealt with by a ‘decided retrenchment of expense, large reduction of taxation, and by a needful reform, commencing with our own House’. He withdrew it later that day, ‘not from any doubt of the truth’ of his assertions, but because it was ‘the most expedient course’, and voted for a similar amendment moved by Sir Edward Knatchbull. He was erroneously listed by The Times as one of the ‘28 opposition Members who supported the address’.
Protheroe continued to press for improvements to the nation’s public archives, securing returns on the work of the commissioners, 26 Feb., 4 Mar., 11 June, urging ‘consideration of a measure for the collection and preservation of the different records scattered throughout this great city’, 3 May, and complaining of the ‘extraordinary want’ of a building for ‘keeping our testamentary records’ and ‘taking care of the records in Doctors’ Commons’ and the ‘papers in Westminster Hall’, 10 May 1830. On 24 May he accused the existing commissioners of ‘the grossest blunders’ in the printing of records and called for the appointment of an entirely new commission composed of ‘competent persons of antiquarian taste and research’ rather than ‘bishops and great officers of state’. He was made a commissioner himself later that year. On 4 Mar. he spoke in support of a Galway petition complaining that Catholics were not permitted to be admitted as freemen and were thus denied the franchise. He called for the opening up of St. James’s, 26 Mar., and Regent’s Parks, 29 Mar., when he asserted that ‘a comparison of our parks’ with those ‘on the continent does not tell in our favour’. He warned against any ‘architectural expense’ and ‘extravagance’ of ‘external decorations’ in the construction of the Pembroke dockyard chapel, 29 Mar. He divided for Jewish emancipation, 5 Apr., 17 May, endorsed favourable petitions from Bristol, 4 May, and argued for the admission of ‘all religious denominations, to a participation of equal civil rights and privileges’, 17 May. He voted for abolition of the Irish lord lieutenancy, 11 May. Citing the overcrowding of London’s burial grounds, he recommended the removal of interments ‘to a place distant from the metropolis’, 13 May. Explaining that he wished to ‘obviate objections to the church’ and ‘see the clergy discharge their duties properly’, he urged that the ‘stumbling-block of tithes ... be set to rights’, 18 May, when he voted for the proper use of Irish first fruits revenues. He presented a petition from Neath for abolition of the death penalty for forgery, 24 May, and voted thus that day, 7 June, 20 July. On 10 June he rebutted attacks by the home secretary Peel on the parliamentary conduct of Joseph Hume. He presented a petition from the Forest of Dean collieries against the coal duties, 11 June 1830.
Protheroe had resolved to retire from Evesham at the 1830 dissolution and accept ‘repeated applications’ to come forward for an anticipated opening at Bristol, with ‘assurances of support’ from ‘the tried friends’ of his father.
Those advisors little know the spirit by which my public conduct has been actuated if they imagine that any personal consequence to myself can possibly influence my attendance or my vote ... It will be a subject of lasting gratification to myself, that the last vote I shall have given in this Parliament, will be in favour of the rights of humanity.
He duly voted for the abolition of slavery that day, jeopardizing his prospects at Bristol. Instead of ‘bowing to the inevitable’, however, he ignored his advisors and stood his ground, declaring that ‘not by expense, not by interest, not by popular tumult, but by moral strength alone shall the triumph be obtained’ and resolving to ‘expend nothing’. After a bitter contest, during which he stubbornly refused to concede defeat and was ‘seriously injured’ in a riot, he was beaten, falling 535 votes short of the 3,378 cast for his nearest rival.
Protheroe was appointed to select committees on the East India Company, 28 June, the House of Commons, 9 Aug., and the West Indian colonies, 7 Oct., 15 Dec. 1831. He called for accounts of the charity funds administered by corporations and details of their distribution in Bristol, 29 June. He encouraged John Cam Hobhouse to reintroduce his bill to open select vestries, which ‘yields, in point of importance, only to the reform bill’, 30 June. He presented and endorsed a Bristol petition for inclusion in the vestries bill, 28 Sept., and argued in its support, 30 Sept., 5 Oct., when he denounced the present system as a ‘great injustice’. He warned of the ‘evils which must arise’ from the ‘establishment of an unlimited number of beer houses in the agricultural districts’, 30 June. He advocated repeal of the soap tax, 1 July. He called for ‘some part of the new building in the British Museum’ to be ‘appropriated for records contained in the about to be demolished King’s Mews’, 8 July. Speaking on Irish education, he defended the role of Catholic priests, 15 July. He was in the minorities for civil list reductions, 18 July, and reappointing the original Members chosen to serve on the Dublin election committee, 29 July. Although ‘pledged to support every measure of economy’, he welcomed the grant to the duchess of Kent, 3 Aug. He secured returns of spirit duties, 5 Aug., when he presented two petitions from the Catholics of Galway for an equalization of their civil rights. He cautioned against delaying abolition of the game laws, 8 Aug. He was in the minority for printing the Waterford petition for disarming the Irish yeomanry, 11 Aug., but voted with ministers on the Dublin election controversy, 23 Aug. He secured accounts of Bristol’s poor rate assessments, 19 Aug. He clashed with Henry Hunt over the conviction of Robert Taylor for blasphemy, 18 Oct., and presented a Bristol petition on the subject, 20 Oct. 1831. He voted for the second reading of the revised reform bill, 17 Dec. 1831, and for going into committee on it, 20 Jan., again gave steady support to its details, but was absent from the division on its third reading, 22 Mar. 1832. He divided for the address calling on the king to appoint only ministers who would carry it unimpaired, 10 May. He declared his intention to introduce a bill to alter the municipal government of Bristol, 14 Dec. 1831, but did not do so. He successfully moved the second reading of the Bristol drainage compensation bill, 17 May 1832. He divided against the government’s temporizing amendment on the abolition of slavery, 24 May. No other votes have been found for that session. He presented a petition for the remission of a prisoner’s sentence in consequence of a cholera outbreak at Bristol gaol, 24 July 1832.
At the 1832 general election Protheroe offered again for Bristol but was defeated in a contest involving two other Liberals and a Conservative. He missed being seated for Halifax by a single vote in 1835, but he was returned there in first place in 1837 and 1841, retiring at the dissolution of 1847. In September 1832 he published a Letter ... to the secretary [of the Records Commission] on the continuation of Sir Francis Palgrave’s edition of the Parliamentary Writs. He continued to campaign for improvements to the public records, particularly those relating to genealogy, and established a substantial archive on his maternal ancestors, now held by the British Library.