Miss-fueling

I'm not sure if this is the right forum but I am sure someone will put me right.
On the way back from the IOM last weekend I had a(nother) senior moment and topped up the T120 with diesel. We managed 100yds before petering out. It would not restart so I called out the recovery people who eventually took me and the bike home.
So I syphoned out virtually 3 gallons of 50/50 diesel/petrol mix this morning, put a small amount of fresh PETROL and swilled that about and syphoned most of that out as well.
Put about half a gallon of petrol in but the bike refuses to start.
I've had suggestions to replace spark plugs and the fuel filter.
Are there any mechanics out there with any pointers for my next steps?

Cheers JB the prize numpty

 

To complete my atonement I thought that I should complete the story.
Having sought advice from the forum I proceeded as follows.
1 I drained the tank as much as possible by syphoning.
2 Removed the tank and flushed it with a little fresh fuel.
3 Refitted the tank and refilled with some Shell V Power.
4 Removedthe spark plugs.
5 Turned the engine over to purge any residual bad fuel in the system.
6 Fitted new spark plugs.
7 Started the bike with a bit of throttle and it gradually started with a fair bit of light smoke which eventually cleared after a couple minutes of higher revs and a eventually settling to a slightly higher tick-over than normal.
8 I then took it for a 30 spin at a healthy pace.
It now starts on the button and runs clean.
Happy days.
For completeness I intend to replace the oil more for peace of mind than anything else.
Hopefully no-one else will have to refer to this. Ever.