The character is Walford's first on-screen gay resident and he featured in the UK's first homosexual kiss on a soap opera, which caused controversy in the British press.

Cashman reprised the role of Colin for the funeral of Dot Cotton (June Brown) for two episodes broadcast on 12 and 13 December 2022.

They move in together and when Dot Cotton (June Brown) discovers they are sharing a bed, she is mortified and spreads rumours that Colin has AIDS.

At a party he meets a new business contact, Guido Smith (Nicholas Donovan), who becomes a romantic interest and moves in with Colin.

This changed by the end of the year, at which time Colin acquired a young boyfriend named Barry Clark (Gary Hailes).

Gay characters that existed were usually farcical, camp parodies, created purely for comic relief, such as Mr Humphries in the situation comedy, Are You Being Served?

[6] Colin was a middle-class, well-meaning, slightly uptight yuppie, and his inclusion was an attempt to portray the gentrification of the East End of London.

Cashman initially resisted playing Colin, but was persuaded by his boyfriend, Paul Cottingham, and after receiving his parents' backing, he accepted the part.

[8] A relationship between Colin and Barry was quickly developed and the residents of Albert Square gossiped in hushed voices about the true nature of their friendship.

[10] Despite the initial negativity, the storyline had a powerful impact on public attitudes and the show's handling of Colin and Barry's relationship was deemed by many gay activists as something of a breakthrough.

[11] Not only did EastEnders brave the wrath of many moralistic viewers and bigoted journalists, but they also exposed that bigotry through the characters in the show — most notably via the inane naivety of local gossip Dot Cotton (June Brown), who erupted into horror and ignorant self-righteousness upon discovering Colin and Barry's secret, and even spread rumours that Colin had AIDS.

[4] Colin was eventually diagnosed with multiple sclerosis, although this fact was kept from him by his doctor for the remainder of the year and he lived out 1988 with the belief that he was in perfect health.

Colin's gay relationship was once again the cause of much controversy in January 1989 when EastEnders aired the first homosexual mouth-to-mouth kiss on a British television soap opera.

The kiss was watched by twenty million people and came at a time when Margaret Thatcher’s government had set forward a moral agenda that urged a return to traditional family values.

The Sun printed the assertion that "Furious MPs last night demanded a ban on EastEnders as the BBC soap showed two men kissing full on the lips".

While still on the cast of EastEnders, Cashman had founded the influential gay campaign group Stonewall and has now given up acting to become a Labour MEP.

[9] On screen, Colin finally learned he had multiple sclerosis and decided to leave Walford to live with his brother and face a rapid decline in health.

[13] Colin shared scenes with Dot Cotton (Brown), but full details of the storyline were initially held back.