If you assign the bond to him then that is a chargeable event and might give rise to a capital gains tax liability, depending on growth on the original investment and whether or not you have had any other capital gains this tax year.
If you have unused CGT allowance of your own and have held the bond for a long time then you may benefit from top-slicing and the tax might not be as much as you think. Do you need to encash the whole bond now? Could you do part this tax year and part next so that you can use your 2016/17 CGT allowance?
Yes, you are right, if it is a gift between spouses then it would not give rise to a chargeable event. And I am sorry that I have misled you talking about CGT - it is income tax not CGT that applies (I was rather tired when I first replied and not thinking straight!)
However, the actual encashment will be a chargeable event. Income tax is deemed to have been paid within the bond at basic rate 20% so as long as the gain (or top slice) when added to his other income for the year doesn't exceed the basic rate threshold then there should be no more tax to pay. But if it is within personal allowance (i.e. nil rate tax payer) then he can't make a reclaim of tax deemed paid.