Who said it would be in a yields lowering environment? That would likely push bond prices up so there wouldn't be a paper loss.
But there are plenty of people.out there who went in on very long dated UK bonds as a 'sure thing', probably regretting it now as the rate and inflation outlook changes. Remember the further out in duration you go the less influence base rates have, its more about inflation and growth expectations.
A reader shares the details of his bet on a UK government bond maturing in 2061 that is hinged on the economic outlook of the UK.
www.ii.co.uk