Clawback of AIA

Is there a mechanism to clawback capital allowances when the business use of an asset falls after it has already received 100% AIA?

Imagine that a sole trader purchases a van purchased on day 1 that is 100% business use and that the full cost is covered by the AIA. In year 2, business use falls to 50% and at the end of year 2, the van is scrapped.

It seems to me that the trader should be entitled to only 75% (average use over the van's life) of the van's cost, but has already received 100% in year 1.