The First Chivalric Virtue
Of the many virtues that are listed as Chivalric virtues, I consider Veritas to be the foundational virtue.
Being honest, especially with yourself, about what you think, and what you feel (and knowing the difference) is an essential first step to everything else. Growth, relationships, improvement, and especially being connected with your true self, all rely upon that internal honesty.
Being honest with other people follows from this internal honesty. There are some people who lie to others as easily as breathing, because they first deceive themselves.
There are some people who think it necessary to be rude to be honest, and that courtesy is a cover for deception. This shows a lack of understanding about the nature of both honesty and courtesy.
Veritas is of inestimable importance today.
We are constantly confronted by spin, distortion, half-truths, and outright lies. Learning to question, to think, to require reason and evidence, begins with self.
To paraphrase both Lenin and Goebbels, and of course Orwell, a lie repeated often enough will come to be believed as the truth.
When we allow ourselves to believe these oft-repeated un-truths merely because of their repetition, we become the subject to the manipulations of the liars. When we repeat these fictions, we become accessories to the crime.

It’s interesting that you put honesty first, as Pride is often considered to be the first and the root of the seven deadly sins. The opposite of Pride, of course, is Humility, which is not (as commonly thought) the same as abasing oneself; rather it is having an accurate view of one’s virtues and failings, that is, being honest about oneself.
Being true to oneself is extraordinarily difficult. It makes for a very good exercise for learning control of one’s mind. For just one facet of this, once you can see yourself truly, one can see others more clearly. Seeing your own faults and weaknesses leads to forgiveness of other’s faults and weaknesses. Once cannot expect others to give more than you, and you must learn to also forgive yourself. This is not to say never try to improve oneself, but how can one improve without a place to start.
This is the starting place which leads to all of the other virtues.