W Corrie Johnstone is an interesting case of someone whose sympathies with the ideas of non-denominationalism espoused by the Brethren eventually led to his joining them. At first a Presbyterian, he was a freelance evangelist in the late 1870s and early 1880s, having declined ordination or a licence to preach as a Presbyterian, ‘preferring to hold himself free for evangelistic work’. He took gospel missions in Victoria, South Australia, and NSW, and in 1876 started producing Words of Grace, a newspaper with evangelistic news, improving stories, children’s items, and gospel messages – intended for handing out on visitation or to contacts, as much as for Christians’ edification. He settled in Christchurch, New Zealand, in the early 1880s, and continued in evangelism with Brethren, mostly within the Exclusive branch, and in writing tracts against Freethought or about Brethren church matters.
However, when in 1876 Johnstone took part in a meeting where Harrison Ord and Douglas Russell baptised by immersion thirty converts from their mission, he was at pains to point out that, although he was happy to wish them well, ‘he [did] not want to be identified with the “Brethren”. At that point his position [was] that of an evangelist willing to cooperate with other Christians of any or all denominations in doing work for Christ.’ 182 Clearly he was already attracted to the principles of fellowship with all Christians espoused by the more ‘open’ Brethren, but not yet affiliated with them.
From "‘Wandering stars’ The impact of British evangelists in Australia" https://eprints.utas.edu.au/12522/2/Revised_thesis.pdf