Imagine that you tell your family that you’ve got an exciting new job and they laugh and don’t believe you.

Imagine that you mention your children to a colleague. First they tell you it’s impossible for you to be a parent, and then to keep your private business to yourself.

Imagine for a moment that every time you have a conversation with someone about a fundamental part of who you are, they deny it. Maybe they don’t believe that it could be true of you. Maybe they don’t believe it is true of anyone. Imagine how it would feel to be told over and over and over that your identity is a lie.

That’s what it can often feel like to talk about being bisexual. And that’s why Saturday 23 September is Bi Visibility Day.

Bisexuality is attraction to people of more than one gender.

Bisexual people experience exclusion not just in public spaces where we might be perceived as too gay, but also in LGBT+ spaces where we can be perceived as too straight (or not gay enough). This experience can be exacerbated by the way that we visually present our gender and/or the gender of our partner. For example, someone who is usually “read” as straight and is in a mixed sex relationship is less likely to experience overt biphobia in public spaces (although they are very likely to feel like their sexuality is invisible in those spaces) and more likely to feel overtly excluded in LGBT+ spaces.

Bi people are often accused of being liars, or greedy, or more likely to be unfaithful to our partners. This is biphobia. These myths and stereotypes contribute to our exclusion in public spaces and LGBT+ spaces alike.

Being bi in public can be an exhausting and isolating experience. When I went to my first Pride event I met a group of gay men who assumed immediately that I was there as a straight ally. It felt like I was pretending to be someone else, or watching Pride through a window. When I corrected them and explained that actually, Pride is as much for me as it is for them – that I am the ‘B’ in LGBT – they seemed almost surprised that Bi people exist.

This year at London Pride I marched with colleagues from the DCLGBT+ and DCLG LGBT+ Allies networks, as well as others from across the civil service and CSRA. I met a bi woman from one department who told me that she nearly didn’t go this year. She was worried that people would think she wasn’t LGBT+ enough to be there because her partner is a man. You don’t stop being a parent when your children leave home. You don’t lose your national heritage when you move to another country.

Bi people are bi whether or not we are in a relationship. Bi people are bi whatever the gender of our partner. Bisexuality is not a phase. It’s not a fetish. It’s not a label with which we identify while we “decide” whether we are straight or gay (although some people do identify differently at different times in their lives, and that’s ok too).

The informal symbol for bisexuality is a unicorn. It’s a running joke in the community that we’re magical, mythical beings that don’t actually exist in reality.

It’s interesting that whenever public figures who have previously been in mixed-sex relationships enter into same-sex relationships, the press too often will say that they are “a lesbian now” or “gay now”. This is Bi Invisibility. Even where bi people are out publically, it can often feel like everyone in the world is trying to rationalise our identity for us as either straight or gay, however many times we explicitly state that we are bi.

When you think for a moment about the cumulative impact of biphobia – of being consistently mislabelled, having your partner misgendered, being told your identity is a phase or quizzed on exactly “how bi” you are – it’s not surprising that studies have consistently shown that bisexual people experience worse mental health than people of any other orientation.

That’s why we have Bi Visibility Day. Because it matters that we can support each other and it matters that we are seen and recognised by our friends and colleagues the way that we see ourselves.

Across the civil service, and in DCLG, we’ve been looking at ways that we can be more bi inclusive. It’s important that we feel safe being out (if we want to be) in our workplaces, and that our LGBT networks (if we choose to engage with them) don’t perpetuate the biphobia that is all too common in the LGBT community more widely. That means not just being implicitly bi inclusive but explicitly welcoming bi members – with our language and our behaviours.

It couldn’t be more important to model bi inclusion, and part of that means not making assumptions about the kind of people we think are usually bi. However engaged you are in the LGBT community, just like every cisgender straight person knows more LGBT people than they think they do, most LGBT people know more bi people than they think they do. Like everyone, bisexual people have multiple identities. Some bi people are men. Some are women. Some are non-binary. Some bi people are disabled. Some bi people are BAME. Some bi people are trans. Some bi people are asexual. Some bi people have mental health problems. Many bi people are more than one of these things.

So let’s put in the work, however we define our sexualities, to challenge biphobia (whoever it comes from) and to actively demonstrate that we recognise, acknowledge and welcome all bi people, always.

In the meantime, this unicorn would like to wish everybody a very happy Bi Visibility Day for Saturday.