Mark will now take you through the results and Erik will describe the forward momentum in the businesses in more detail.
Mark H. Armour
Thank you, Chairman, and good morning. I'm pleased to report a very strong set of results. Underlying revenue growth was 5%, excluding a 2% benefit from buying the exhibitions cycling in. That is exhibitions that took place this year, but not last year, underlying revenue growth was 3%. Underlying operating profit growth was 7%.
Including acquisitions and disposals, overall revenue was up 5% at constant currencies and in sterling. In euros, overall revenues were up 12%, reflecting the weakening of the euro first half from first half. The adjusted operating margin increased 1.1 percentage points to 27.7%. Adjusted earnings per share were up 11% for Reed Elsevier PLC at 24.7%, and up 18% for Reed Elsevier NV at EUR 0.47, and it's good to hear the bank chimed in.
On constant currencies, adjusted earnings per share were up 10%. The growth in reported EPS, that is including amortization of acquired intangible assets and disposal gains was 52% for Reed Elsevier PLC, and 57% for Reed Elsevier NV.
Cash flow was strong, with a 52% conversion of adjusted operating profits into cash in the first half, and 94% on the last 12 months basis. Our balance sheet is in good shape with net debt-to-EBITDA of 2.3x on a pensions and lease adjusted basis, or 1.7x on an unadjusted basis.
Interim dividend is up 6% for Reed Elsevier PLC and up 18% for Reed Elsevier NV. The significantly higher increase for Reed Elsevier NV reflects the weakening of the euro against sterling since last year's interim dividend announcement.
I'm presenting the figures today, as usual, in sterling. The same charts with euro figures can be found in the appendices of the presentation. Reported revenues and adjusted operating profits were up 5% and 9%, respectively, in sterling, and up 5% and 8%, respectively, constant currencies.