In consequence, he was posted to New South Wales in September 1841[1] the family traveling by the barque Sir Edward Paget which had departed from Cork on the 26 October 1841.

In July 1843 Marlow and the crew of the engineer department boat, came to the rescue of an intoxicated fisherman who fallen from his dingy in the harbour during a squall, saving the fellow from drowning.

Captain Marlow embarked with the officers and troops of the 99th Regiment, for Auckland, New Zealand, on the British Sovereign on 18 May, for the emergency that had broken out at the Bay of Islands in March.

Beating up the Bay of Islands before daylight, under hard sqaulls and poor weather, British Sovereign soon struck the Brampton reef, damaging the bottom, losing the false keel and rudder; the colour union down and firing muskets.

Thomas Bernard Collinson noted in 1853: "Captain Marlow considered that 12-pounder guns and 5-1/2 inch howitzers would be required to make a breach in Ohaiawai pah.

"[26]: 49–50  At some point, it had been suggested to Despard that a breach might be effected by powder bags; Lieutenant George Phillpotts, RN, volunteering to carry out the hazardous task, was snubbed.

[27] That day, after the 32-pounder had fired the last of its 26 shots, and with Heke's morning attack still fresh in mind, Despard put his opinion to council that the palisades had been loosened and an assault may be successful.

[26]: 62 [28] Marlow's advice, and Bennett's earlier assessment, proved correct when the soldiers suffered considerable losses when assailing the pā without success that afternoon.

[29][30] In a despatch to Governor FitzRoy the following day, 2 July, Despard acknowledged the assistance of Marlow and his volunteer pioneers who had laboured under the same inefficiency as the artillery.

[31] Upon Marlow's drawings and description of Hōne Heke's pā sent to home to England, in August–September 1846, the Royal Engineers erected part of a stockaded work based upon it, to the left of Chatham Lines, so as to establish the best mode of breaching it by bags of gunpowder.

[32]: 111–113 [33][34] Before daylight on 16 July 1845, with Despard, 200 infantry, two guns and a proper proportion of artillery, with Marlow and his pioneers, marched from Waimate to engage one of Heke's principal chiefs, Te Haratua, and warriors, at his Pakaraka pā, some six miles away.

Marlow, Lieutenant Leeds, HEICN, and Johann Pieter (John) Du Moulin, Commissariat, surveyed and sketched pā for the record.

[26]: 27  The following months saw the marriages of two daughters—Catherine Victor to Philip Turner, Deputy-Assistant-Commissary-General, on 13 June, and Sophia Sewell to William Plummer, Barrack Master, on 1 September.

For his efforts, Marlow was awarded rank of brevet major on 7 July 1846[45] Colonel Henry Despard, Colonel Robert Wynyard, and Captain Graham, RN, were appointed Companions of the Most Honourable Military Order of the Bath;[46] Captain Denny, 58th, Lieutenant Wilmot, RA, also received brevet rank; and Tāmati Wāka Nene received a pension of £100 a year.

[47]: 71 The expanding military presence in New Zealand placed Marlow and his clerk of works, George Graham, to correspondingly accommodate their needs: In Auckland, the construction of commissariat store (1845), officers quarters (1846),[48] magazine (1846) and cells for Fort Britomart; a road from Mount Eden quarry; and wooden barrack buildings and extensions, cook house, wash house, privies (1845–), military hospital and out-buildings (1846–47), and enclosing basalt stone wall (1847–50) for Albert Barracks.

[49]: 348–350, 467 In Auckland, the fencible settlements were also designed and laid out, including the construction of 100 ft sheds and out-buildings as temporary barracks, single and double cottages.

[51] Following Lieutenant Collinson's arrival in September 1846, and his assignment to the southern region, the construction of temporary wooden barracks and powder magazine for Mount Cook in Wellington (1846),[52] and stockades and blockhouses (1846–) for Wanganui.

Colonel Daniel Bolton, RE, with 13 sappers and miners and the first contingent of fencibles, arrived in Auckland on 5 August 1847, relieving Marlow as Commanding Royal Engineer.

[49]: 466–470  Having sold up household items from their Emily Place residence over the following months, on Wednesday, 1 March 1848, Major Marlow, Catherine and youngest daughter Charlotte Augusta, left for the aptly named schooner Cheerful destined for Sydney and England.

Upon their departure a group of about 100 Māori employed by the Engineer Department assembled on the beach to show their respect with three hearty cheers and a presentation of highly valued feathers given to men of distinction.

[57] Soon after promotion to lieutenant colonel on 1 April 1852,[58] granddaughter, Annah Kate Burke, died on 3 October 1852, and was buried with her grandmother at St Canice's Cathedral Graveyard.

[59] Back in England since arrival on the Orinoco in May 1857,[60] Marlow returned home to Alverstoke to live with his sister and niece at Anglesea Lodge,[61] then to nearby Knapp Green in 1861,[62] retiring from service on full pay in late March 1862, with[63] promotion to honorary rank of major general, on 3 April 1862.