|2017*† £m||2018† £m||2019 £m||2020 £m||2021 £m|
|Intelligence & Communications||200.5||211.1||224.8||241.0||241.3|
|Critical Detection & Control||245.4||237.7||247.6||227.0||214.0|
|Underlying operating profit1|
|Intelligence & Communications||18.8||21.6||30.2||33.5||37.9|
|Critical Detection & Control||42.0||38.3||35.5||34.0||32.3|
|Total underlying operating profit1||120.1||112.7||118.2||126.1||129.6|
|Profit before tax||60.6||42.6||91.0||103.7||82.7|
|Profit after tax||48.9||32.4||74.6||83.8||66.9|
|Underlying operating cash flow2||116.5||89.3||86.8||116.1||111.5|
|Free cash flow3||65.3||67.6||64.7||99.4||90.7|
|Net debt at year end4||(74.5)||(157.5)||(154.8)||(85.8)||(40.0)|
|Underlying earnings per share (p) 5||116.7||109.5||119.5||130.6||135.7|
|Dividend per share (p)||49.6||51.6||54.2^||56.9||16.2**|
|Average employee numbers||4,172||4,119||4,089||4,253||4,531|
The operating segment split for 2017 to 2019 has been restated to reflect the new segments that became effective from 1 January 2020.
1 Underlying operating profit is before amortisation of intangibles arising on acquisition, acquisition and disposal related costs, significant legal charges and expenses and, for 2018 and earlier, the S3 programme and impairments. See note 2. Underlying operating margin is the underlying operating profit as a percentage of revenue.
2 Underlying operating cash flow is cash generated by operations, less principal payments on finance leases, less net capital expenditure and R&D, and excluding cash outflows from acquisition and disposal related payments and significant legal charges and expenses and, for 2018 and earlier, the S3 programme. See note 2.
3 Free cash flow is before dividends paid, acquisitions, disposals and financing.
4 Net debt is loans, overdrafts and finance lease liabilities less cash and cash equivalents. See note 27.
5 Underlying earnings per share is before amortisation of intangibles arising on acquisition, fair value movements on derivatives, acquisition and disposal related costs net of contingent consideration adjustments, gain or loss on disposal, significant legal charges and expenses and, for 2018 and earlier, the S3 programme, impairments, GMP equalisation and defined benefit pension finance charges and in 2018 the loss on closing out a foreign currency derivative contract. See note 12.
* Not prepared under IFRS 15.
† Not prepared under IFRS 16.
^ When including the 2019 final dividend that was withdrawn as a precautionary measure due to the Covid-19 pandemic, and paid on 18 September 2020 as an additional interim dividend.
** Under the terms and conditions set out in the announcement dated 16 August 2021 (relating to the recommended cash acquisition of Ultra by Cobham Ultra Acquisitions Limited), no 2021 final dividend will be paid to shareholders while the acquisition remains conditional on obtaining certain clearances, including UK Government approval. Consequently, the total full year dividend is unchanged from the interim dividend of 16.2p.