Help with a seized bolt/washer (rear wiper part)

[R1gtr]

Hi guys I am hoping someone can maybe help save face with my girlfriend, her Renault Clio had a broken rear wiper arm and she popped in to the local Renault Dealer who removed the broken plastic part and sold her a new arm.

They could not however remove the metal part that connected the old arm to the car from the rod that comes out from the motor.
They said it would be a workshop job and approx 100 pounds.
Obviously I told her "don't be silly,it's a two minute job, I will sort it for you".

However for the life of me I can't get it off, the final pic shows the new arm with a new version of the offending bolt ready to go on if I can get the old one off. It's not threaded so in theory should just slide off but a pair of pliers and a wrench have not moved it.

Any ideas on how to get it off so I don't lose face with my Girlfriend?
Thanks in advance

[R1gtr]

Thanks guys, I thought cutting it may be the only way to do it, will give it a try on thurs and report back

[R1gtr]

The wiper cracked in the plastic surrounding the seized bolt so it was slipping up and down, The garage just spread the crack to remove the arm but left the metal bit. They said they can fix it but 100 seems a bit expensive, will try a hacksaw or dremel on thursday and see how I get on.
I did not want to be too heavy handed in case I broke the whole mechanism

[R1gtr]

Nut splitter looks a good bet, little bit concerned it would crush or damage the 'rod' that the nut is stuck on?

[R1gtr]

Many thanks chaps, hopefully the 100 quid she has saved will be spent on treating me! Will post back once I have done it