The Duchess returned to Erdem for tonight’s celebration of Swedish culture.
The event was at Fotografiska Galleries. Weather permitting, the Royals were going to get to the event by boat to allow “The Duke and Duchess to take in the views of Stockholm by night as they pass around the harbour.” (That info via Kensington Palace.) From the look of things, I don’t know if the weather cooperated or not.
Here is a brief video by Richard Palmer showing the royals arriving at tonight’s party.
Royals reunited tonight at a reception for stars of Swedish film, music, the arts, and sport. pic.twitter.com/3QyrVnls3v
— Richard Palmer (@RoyalReporter) January 31, 2018
More from The Daily Mirror:
The couple attended the event at the Fotografiska Gallery, which boasts stunning views over Stockholm and were joined by guests representing the world of music, film, television, art and sport.
The Duchess and Crown Princess Victoria greeting each other.
This is the last formal engagement for the foursome, I believe.
Kate mingling with guests.
Here it looks like everyone is viewing abstract works.
Kensington Palace said the function this evening was a celebration of contemporary culture.
Now to what Kate wore for this evening’s engagement, the Christina Blue Velvet Bell Sleeve Dress by Erdem.
The dress is a runway piece, shown as part of the a/w 2107 collection.
It is a cotton-blend velvet-devoré, described as being medium weight. It features a high neck with a fitted bodice, flared cuffs on the long sleeves, fluted godet hemline inserts, and a concealed back zipper. Long sold out, you can still view details about the dress via this link to Browns. 
This is from a column by style writer Olivia Buxton Smith of The Telegraph:
Thus far on her Nordic trip, the Duchess has made a characteristic display of sartorial diplomacy, mixing big British designers like Burberry and Erdem with Swedish labels like outdoor brand Fjallraven; a pattern that has continued this evening.
The Duchess has opted for another sleeved Erdem gown tonight, not dissimilar to the one she wore for the black tie dinner hosted by the British ambassador yesterday, only this one is made from blue velvet. A glamorous and practical choice, considering Sweden’s subzero temperatures.
Kate wore a new coat by a designer who has long been a favorite for Swedish Royals, and many others, Ida Sjöstedt. The piece is from the a/w 2018 collection.
Heaven QRF on Twitter shared word that Princess Sofia has also worn this design.
Laura, who follows the Swedish Royal Family, points out that “Ida Sjöstedt has been worn many times by the princesses. Sofia’s 2014 Nobel Prize dress and wedding dress were custom Ida creations.”
Crown Princess Victoria wore Ida Sjöstedt yesterday; both her coat and her dress are by the brand.
Below, the designer’s Instagram with her reaction to Kate wearing one of her designs.
As noted in the Instagram post, it looks like Kate brought back the Troy London faux fur collar and cuffs first seen yesterday. (I think someone commented on this, and I’m thrilled you did because I didn’t really notice the cuffs!)
Kate accessorized with her Gianvito Rossi D’Orsay Suede Sandals. 
She had on a pair of statement earrings, large hoops covered in diamonds. They appear to be the Robinson Pelham Aspen style from the jeweler’s Oxygen collection. 
The earrings are done in 18K white gold and diamonds (£4900, about $7000). The company is a favorite of Kate and several of the Middletons. Among other things, the Duchess’s wedding earrings are by Robinson Pelham. Many thanks to Madhu on Twitter for her terrific ID, yours truly was coming up emptyhanded!
Kate’s hair was partially up.
We’ll leave you with this shot of the Duchess.
And tomorrow’s schedule.
Larissa
Sunday 4th of February 2018
Yikes, this is quite possibly my least favourite look ever on Kate. I like her hair, with the bun sitting a bit higher than usual, and the umbrella. That's it.
I'm not a fan of velvet clothing at all and am sad to see it's making a comeback (although William's shoes the other night were nice - opera slippers are probably the only place I'm glad to see velvet!). Combined with this pattern and the big sleeves, the whole dress is a mess. The strappy pumps make the proportions awkward in combination with the mid-calf dress length. The earrings seem unusually big and a little blah. The coat would be nice without the unnecessary fur additions, or if Kate had at least stuck with only the collar like Sofia did.
Erg. Luckily I'm writing this long after the fact so I can just move on to the next post and forget about this disaster!
Lisa
Saturday 3rd of February 2018
I'm crazy about the earrings, they are amazing! I'm sure the dress is lovely in real life, problem is that velvet doesn't look good in pictures due to the flashlights...
TravelingBlush
Friday 2nd of February 2018
I have to laugh at all the curtains comment. In our side of the world, curtains with prints like these will elicit the opposite comments, i.e. why are you using your dresses as curtains.
Aah the quirks of geography.
Love the whole styling and makes me nostalgic for velvet - no chance in the tropics.
Mel
Friday 2nd of February 2018
Kate looks lovely. Evening wear for a pregnant lady is always difficult. This dress does look nice for a pregnant evening event. It has shine and fits nice around to rounding belly. Lol. The colour is fabulous. Kate does like bold patterns. The earrings super fabulous. She looks fantastic and can not be compared to Princess Victoria. (The one has a sexy figure and the one must try to look good).
lawgirlnyc
Thursday 1st of February 2018
She's being fashion-forward again! So a "YAY" from me, even though I don't particularly like Erdem. Ok, I dislike Erdem. The ankle straps on the shoes - eek. I think this establishes how incredibly difficult it is to pull off ankle straps. The DoC has legs like a barbie, but these don't look great. The interesting footwear on the models elevate the dress. I wish the DoC would try more interesting footwear. Overall... good for her. She wears this with confidence and pulls it off.