Early in the novel, Clarissa thinks disdainfully about something Peter Walsh—who loved her and wanted to marry her—said to her a long time ago, before she married Richard Dalloway. As she angrily recalls what he said, the narrative makes use of situational irony to draw attention to the expectations Clarissa used to have for herself and the ways in which she has inadvertently become the very thing she didn't want to become:
How he scolded her! How they argued! She would marry a Prime Minister and stand at the top of a staircase; the perfect hostess he called her (she had cried over it in her bedroom), she had the markings of the perfect hostess, he said.
Ironically, Clarissa thinks angrily about this comment about her becoming a "perfect hostess" while running errands in preparation to host a party. Furthermore, the Prime Minister will be attending this party, giving Peter Walsh’s words something of a prophetic quality. She hates that he sees her as someone who cares so much about status and about hosting parties, but here she is, hosting a party for people of high status. She has, in other words, become exactly what Peter Walsh predicted. In fact, it's possible that she reacted so strongly to his accusations all those years ago because she, too, privately suspected that she would lead this life but resented him for saying as much.
There's some dramatic irony to the fact that Richard decides to give Clarissa flowers as a way of expressing his love. What he doesn't know is that Clarissa has already bought flowers herself, but readers do know this. In fact, the very first line of the novel announces Clarissa's intention to buy flowers: "Mrs Dalloway said she would buy the flowers herself." As such, the entire time Richard is walking home and proudly thinking about the grand statement he's making by bringing Clarissa flowers, readers know his gesture won't be all that meaningful. In this way, the narrative subtly pokes fun at him as he excitedly prepares to present the flowers to his wife:
But he wanted to come in holding something. Flowers? Yes, flowers, since he did not trust his taste in gold; [...].
Richard thinks this while standing next to Hugh Whitbread and watching him select jewelry for his own wife. He thinks that by choosing to give Clarissa flowers, he will circumnavigate the fact that he has no idea what kind of jewelry to get her. And yet, buying her flowers only further emphasizes how out of touch he is with his wife. After all, readers know that Clarissa already bought flowers earlier in the day, and though it's perhaps understandable that Richard might not know this, it does suggest that he doesn't have a very good idea of what she does during the day. And this, in turn, only accentuates the "gulf" between them.
Richard brings Clarissa flowers and plans to express his love for her. But when he sees her, he finds himself unable to do so, and Clarissa ends up thinking about how emotionally distant people—including spouses—can be from one another. Richard’s attempt to make a romantic connection with his wife thus only ends up making her feel less connected to him, leading to a perfect example of situational irony. Richard intended to make a gesture that brought him and his wife closer, but the gesture itself ends up making Clarissa feel like there is a "gulf" between them. As he leaves, she thinks:
And there is a dignity in people; a solitude; even between husband and wife a gulf; and that one must respect, thought Clarissa, watching him open the door; [...].
Of course, it's worth noting that Clarissa isn't upset by her interaction with Richard. It's just that she starts thinking about how unknowable people are—everyone, she reflects, has their own private life that is very difficult for others to understand. Although it's ironic that she ends up thinking this after Richard tries to connect with her, it makes perfect sense, considering Richard's complete failure to actually express his feelings. His original plan was to give Clarissa flowers and tell her that he loves her, but he found himself incapable of saying "I love you." Instead, they spoke about ordinary things, and though he leaves feeling as if he has, in some way, conveyed his affection, it's unsurprising that Clarissa feels rather confounded by her husband, since his behavior would surely be quite hard to read in this situation.
And yet, Richard himself seems rather pleased. He thinks he has expressed his love for Clarissa "in so many words," but all he has done is give Clarissa flowers. As such, there's also some dramatic irony at play, as readers understand that Richard's gesture has failed even though he himself is completely unaware of this fact—he thinks he has more or less accomplished what he set out to do. Because readers have access to Clarissa's thoughts, though, they know that this isn't necessarily the case.
When the Prime Minister arrives at Clarissa Dalloway's party, he's not nearly as impressive as one might expect him to be. Given how much importance everyone seems to imbue him with, it's ironic that he himself doesn't seem very important at all:
One couldn't laugh at him. He looked so ordinary. You might have stood him behind a counter and bought biscuits — poor chap, all rigged up in gold lace.
This description of the Prime Minister is mockingly disdainful, as the narrator suggests that he looks like he belongs "behind a counter" selling people biscuits. And yet, he's also decked out in "gold lace," which further emphasizes the irony at play: he's technically important and is even dressed in fancy clothes, but he still seems quite drab and ordinary.
And yet, the novel uses this moment to satirize the superficial nature of British high society. When the Prime Minister arrives, nobody makes much of a fuss. "Nobody looked at him," the narrator notes, adding that everyone simply goes on with their conversations. But it's also the case that everyone at the party does register the Prime Minister's presence:
They just went on talking, yet it was perfectly plain that they all knew, felt to the marrow of their bones, this majesty passing; this symbol of what they all stood for, English society.
Even though the Prime Minister is, in reality, an extremely underwhelming figure, everyone at Clarissa's party is in awe of him. In this way, the novel satirizes the ridiculous, elitist obsession that so many of the characters have with "English society" and the respect it supposedly commands. The Prime Minister himself ironically falls short of their expectations, but this doesn't stop them from getting excited about the mere idea of being in proximity to the kind of patriotic power he represents.
