Can previous historic losses offset profits made in the current tax year in relation to capital gains tax?

Yes you can, provided that you have reported your losses to HMRC.

Losses don't have to be reported immediately but must be claimed within 4 years of the end of the tax year in which the disposal occurred ('disposal' usually means sale, e.g. sale of shares).

You would normally report losses and gains via a Self Assessment tax return.

Technically, it doesn't actually change the tax free allowance (called the Annual Exemption Amount) on capital gains, but it does have the effect in reducing your tax liability.

GOV.UK Capital Gains Tax/Losses