Don't over think it

[Gizmo3]

Next week I'm heading to London for a three day work conference. The BIG conference day is the Thursday.
Today I received an offer of an interview, and yes, Sod's Law it's in Leeds (home) on the Thursday at 9am.
In the job advert (and interview offer email) it explicitly notes that the recruitment day is on Thursday and if you can't make it you will be withdrawn from the process.
This is a job I've wanted for years, that I've tracked/followed for a long time waiting for the opportunity...
I've been in current company 2.5 years with no sickness or absence.
Is it as simple as go to the Tuesday and Wednesday of the conference and then make an excuse not to attend on the Thursday?
If so, what's a "safe" reason?
i feel really uncomfortable being in this position.

Thanks everyone. I'm not comfortable with funeral or serious family/medical issue. The more vague the less believable I suppose, but going down for two of three days shows overall willing.

The job advert strictly says do not apply if you can't make the recruitment day and interview slot. I am certain if I say I can't make it or ask for an alternative they will be firm and blunt and say no.

One friend suggested Jury Duty, again I don't know the technicalities having never done it before so wouldn't feel confident... and Law of Sod says I genuinely get the call up later down the line ;-)

I'd fall ill on wed afternoon, maybe catch them just before end saying you are unwell and need to go , say you want to set off now in case you need to stop a few times. Be vague stomach issues. then you can legitimately check out of hotel and set off home.