Postpublished at 10:30 British Summer Time 7 June 2019
I'm expecting Peter Hickman to have built a bit of a lead at the Bungalow.
Hickman and Harrison in another duel
Get involved at #BBCTT
Peter Hickman looking for fourth win of the week - has bike issues
TT fortnight hampered by weather but all races set to be completed
Tom Rostance
I'm expecting Peter Hickman to have built a bit of a lead at the Bungalow.
If you wonder just how fast these superbikes are - both Dean Harrison and Peter Hickman went through the Sulby speed trap at 192mph.
That's a normal public road for 99% of the year, remember. HGVs making deliveries on it, buses carrying kids to school...
Allow X content?
This article contains content provided by X. We ask for your permission before anything is loaded, as they may be using cookies and other technologies. You may want to read X’s cookie policy, external and privacy policy, external before accepting. To view this content choose ‘accept and continue’.
Hickman back into the lead - by just 0.118 of a second. Incredible consistency.
Lap one
Dean Harrison has now got past Conor Cummins on the road as the first riders reach Ramsey hairpin. Now they will start the mountain climb, where Peter Hickman has been so fast.
Well they're all fast, but you know what I mean...
The riders reached Ballaugh five seconds quicker than they did on the opening lap of the Superbike TT on Monday.
Fast.
Richard Petrie
BBC Sport NI at the Isle of Man TT
There were some mighty sweet sounds filling the air as the bikes leave us here at the Grandstand.
Among them the mighty Norton of John McGuinness and the exotic £250,000 MotoGP-based RCV Honda piloted by Michael Rutter.
At Ballaugh Bridge, it's Dean Harrison who goes into the lead! The lead is 0.185 seconds from Peter Hickman.
Are we in for another stone cold classic like last year? These same two chopped and changed the lead all race until Hickman nicked it with that first 135mph lap.
Hickman and Harrison are about five seconds faster than anyone else through that first section of the race. On another level.
But there is so much distance left to run.
Splits at Glen Helen on lap one
Hickman leads by a third of a second! Nothing in it.
Dean Harrison is already within sight of Conor Cummins on the road. He's eaten up the bulk of the 10 seconds between the two at the start at Glen Helen.
The story of most of the races last year was Dean Harrison flying through the first two thirds of each lap, and then Peter Hickman puling back oodles of time over the mountain. Let's see.
You are looking at a lap time of under 17 minutes on these 1,000cc machines by the way. That's 37.7 miles - you do the maths.
Pre-race favourite Peter Hickman is away. Sadly there's no Lee Johnston, who has had some late mechanical issues with his BMW.
There goes Michael Dunlop - could this be an incredible 51st TT win for the incredible family?
Dean Harrison is off on his Kawasaki, followed by the super loud Norton of John McGuinness.
Conor Cummins screams away from the line on his Honda Fireblade!
He'll be doing 175mph before you've read this sentence.
The six-lap Senior TT is go. Go well everyone.
There are four former Senior TT winners in the field today - John McGuinness with seven, Michael Dunlop with three and one apiece for Peter Hickman and Ian Hutchinson.
Manxman Conor Cummins will lead the field away - he's bike number one.
TT legend John McGuinness: "It's an early start! Good conditions though, best of the week.
"This will be tough. I'm super nervous again but we'll give it a go."