Straight line method means the same amount depreciated every year.
So if lets say we bought and asset for £10,000, annul depreciation would be £2.200 (22% of cost). However 5 years total depreciation would be £11,000 leaving asset at a negative carrying value/loss.
At the end of year Year1 CV would be £7,800 and Accummulated depn. £2200 Y2 CV £5,600 Acc. depn. £4,400 Y3 CV £3,400 Acc. depn £6,600 Y4 CV £1,200 Acc. depn. £8,800 Y5 CV -£1,000 Acc. depn £11,000