Conditionally Hide a Link in a Metabox Vioew if the Custom field is empty?

Hi people!
Please can someone help me with this code??
I have a metabox view with a link to "Download Brochure" that I need to conditionally hide if the custom field "{{ post.upload_presentation }}" is empty:

Here is my view code:

{% set relationship = attribute( relationships, 'venues-to-galleries' ) %}
{% for post in relationship.from %}
<div id="div_block" class="grid-venue-properties">
{% for clone in post.venue_info_group %}
<div class="pad--xs grid-venue-properties__item">{{ clone.venue_item }}</div>
<div class="pad--xs grid-venue-properties__item">{{ clone.item_description }}</div>
{% endfor %}
</div>
<br>
<a class="ct-link-button download-brochure__btn" href="{{ post.upload_presentation }}" download>Download Brochure</a>
{% endfor %}

So I think that this part needs wrapping in some type of if/else code:

<br>
<a class="ct-link-button download-brochure__btn" href="{{ post.upload_presentation }}" download>Download Brochure</a>

Unfortunately I am not a coder so all my atetmpts keeping breaking my site!