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If you were to become resident in the UK for tax purposes, then split year treatment will apply in that your earnings from the date of arrival to end of tax year i.e 5 Apr 2017 would be chargeable to UK income tax.
Your overseas earnings before coming to the UK would not be chargeable to UK income tax.
There is no reason why earlier years would be scrutinized if you were non resident and did not have any income arising in the UK that has not been disclosed e.g. income from property in the UK.
More information on split year treatment under Statutory Residence Test on pages 3 and 4 here
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