The right-back started the World Cup as Holland's first choice in the position, and while Dirk Kuyt was preferred as a right wing-back in some of the later games, Janmaat arrives with extensive experience and a lofty reputation.
His arrival makes it six transfers so far this summer - quite a tally given Mike Ashley's refusal to sign anybody permanently during the two previous transfer windows.
Transfer likelihood rating: 10/10
Will Janmaat's arrival signal the end of Newcastle's spending this summer? Hopefully not, as the Magpies could still do with another centre-forward and arguably a new centre-half before they're fully set up for next season.
Clement Grenier has been a target for quite a while now, and the French media were reporting yesterday that Newcastle had an offer turned down for the midfielder earlier in the summer.
That was before deals were completed for Siem de Jong and Remy Cabella though, so it's extremely unlikely that Newcastle will go back to Grenier, even if Lyon were to reduce their demands.
And given that Grenier has previously stated that he wants to move to a club in the Champions League, that's one move that looks dead in the water.
Transfer likelihood rating: 1/10
Will Fabio Borini be a Sunderland player by the end of the transfer window? God knows. But it increasingly looks as though we're going to be talking about the Italian every day as his future remains as uncertain as ever.
Yesterday's development was that Liverpool slapped a £12m price tag on the head of the striker (wouldn't it help transfer negotiations if players were actually forced to walk around with price tags hanging off them, so everyone instantly knew what they were valued at? Mind you, Harry Redknapp would still end up paying £3m more than he had to).
Sunderland are reportedly willing to pay £8m up front, but Liverpool are adamant they're going to have to go to £12m to sign Borini.
It's a saga that's run since the end of last season, but it's one that Sunderland could do with resolving quickly as they look to make progress in other areas.
Transfer likelihood rating: 6/10
'Sunderland to sign Rodriguez'. Sadly, it's not James Rodriguez - now that would be quite a story - but Atletico Madrid winger Cristian Rodriguez would still represent a pretty decent addition.
The Uruguayan is looking to leave Atletico this summer after barely featuring under Diego Simeone last season, and the respected Spanish daily Marca claim Sunderland are one of the clubs to have registered an interest.
Gus Poyet will certainly be aware of a player who has won almost 80 caps for Uruguay, and the Black Cats boss is definitely looking to add creative attacking talent during the current transfer window.
It's still early days, and other clubs could well become interested if Rodriguez is given the green light to leave Atletico. At this stage though, Sunderland certainly look to be interested.
Transfer likelihood rating: 6/10
I used to live near Bishop Auckland, so I can quite confidently state that it's not somewhere where you expect to find Spanish Second Division teams wandering around. Not down Newgate Street anyway.
But come August 7, Bishop's Heritage Park ground will play host to a pre-season friendly between Sunderland and Real Betis. Let's hope the pubs round the Market Place have stocked up on sangria....
Free Jelle Vossen might not have quite the same ring as Free Nelson Mandela, or come with a nice catchy tune, but it's a social media campaign that has caught the attention of Teesside and Belgium alike.
A response to comments from Vossen where he spoke positively of a potential move to Middlesbrough, Boro fans have been using Twitter and various similar sites to strike up a campaign urging Genk to allow the striker to move to Teesside.
It's all been good knockabout stuff, but it'll only have the desired effect if Boro stick a considerable amount of wedge on the table and, at the moment, that simply hasn't happened.
There's been a number of inquiries, and Boro would still like to add the Belgian striker to Kike, who signed last week.
But with Genk having turned down an offer of around £4m last summer, it's going to be interesting to see how high Boro are prepared to go this summer as they look to strengthen their attacking ranks.
Transfer likelihood rating: 5/10