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Brown has said he knows nothing of pre-contract...
... but on the other hand, if Celtic did announce they have him on a pre-contract, they would be admitting that they have breached the terms of McCart's release. Sure even though he won't technically sign until his contract is up, he has still been approached and agreed terms before then, so they are foul of any agreement with Motherwell.
Edit: We will get a develompment fee at a tribunal anyway... I would be highlighting the figures involved in the sales of McFadden, Clarkson etc at that