I have just taken the following extract from the Royal Navy website -
"The next step in preparing Portsmouth as the home of the biggest warships ever built for the Royal Navy begins this week.
A specialist rig begins six weeks of drilling on Friday, sampling the sea bed in the harbour and in the Solent.
The tests will pave the way for major dredging work in a couple of years’ time allowing the 65,000-tonne HMS Queen Elizabeth and Prince of Wales to safely and easily enter harbour.
The two flagships are 10,000 tonnes heavier than the last traditional-style carriers to serve the Royal Navy – HMS Ark Royal and Eagle, which paid off in the 1970s – and much larger than any current warship based in Portsmouth.
The existing channel used by ships needs to be widened and deepened to accommodate the new carriers. The berths in the base itself need to be excavated and a suitable turning circle provided in the north of the harbour – the draught of the sisters will be 11 metres (36ft)."
Obviously these ships will be the largest ever that have served with the RN, but interestingly the battleships QUEEN ELIZABETH and VALIANT both drew 34.7ft (full load (36,565 tons)) and VANGUARD 35.7ft (full load (46,500 tons)) which is only a fraction less than the CVFs.