pre_text: 2 Alternative performance measures continued Net debt to earnings before interest, tax, depreciation and amortisation (EBITDA) To assess the size of the net debt balance relative to the size of the earnings for the Group, we analyse net debt as a proportion of EBITDA. EBITDA is calculated by adding back depreciation and amortisation of owned property, plant and equipment, software and development to adjusted operating profit. Net debt excludes IFRS 16 lease liabilities. The net debt to EBITDA ratio is calculated as follows: The components of net debt are disclosed in Note 24.
table: 2019 2018
table: £m £m
table: Adjusted operating profit 282.7 264.9
table: Depreciation and amortisation of property, plant and equipment, software and development 34.3 32.9
table: Earnings before interest, tax, depreciation and amortisation 317.0 297.8
table: Net debt 295.2 235.8
table: Net debt to EBITDA 0.9 0.8
question: Analyse this data from a financial earnings document. What was the change in net debt from 2018 to 2019?