“She has extended the invitation multiple times but has yet to set a date for the welcome party. “You are part of our family, your future is in our union, and our union is not complete without you,” Ursula von der Leyen, the European Commission president, last year told Ukraine and the nine other countries queuing patiently for EU membership,” recalls London ‘The Guardian’.

What would be the impact on the EU budget, already under pressure? Would Poland, Greece or Hungary be happy to go from net beneficiaries of EU funding to net contributors? Would Germany and France be prepared to contribute more?

Would MEPs have to budge up on the benches to make space for more politicians from new states in what could be the world’s biggest parliament? Would the political balance swing to the left or the right?

Any one of the 27 member states can veto the accession of another country, making domestic politics a strong factor in decisions as to who gets into the EU and who does not. If any one state finds any of these questions unpalatable to its electorate, it could impede accession.

“It is very late that member states seem to have woken up to the idea that they will have to reform internally,” says Steven Blockmans, the director of research at the Centre for European Policy Studies (CEPS).

The war changed all of that. As one diplomat said: “Enlargement is not only back on the agenda but it is back as one of the top three issues the leaders are dealing with.”

Ukraine and Moldova were added last summer to the queue of official candidates comprising Albania, Serbia, Kosovo, Turkey, Montenegro, North Macedonia and Bosnia and Herzegovina, with Georgia in the active application process. Kosovo is in a stabilisation agreement with other Balkan states to help get it further on the path.

The European parliament president, Roberta Metsola, has called for official negotiations for entry to the EU to be started with Ukraine and Moldova next year, and there is recognition at the top of the commission that attention must also now be focused on the questions holding up accession for western Balkan countries.

Launching the Spanish presidency of the EU last month, Von der Leyen said: “We have to discuss how the decision-making process will look. We have to discuss how the common funding that we have will be allocated: what are common policies that we follow up? These are very principled questions we have to ask each other. We have to address them as soon as possible, because it will take us time to come to a conclusion.”

While Ukraine and Moldova are now frontrunners, one senior EU diplomat cautioned that nothing would happen to expedite the process until there was greater clamour from within the EU. “Nothing will happen until there is maximum political pressure. Why would member states agree to enlargement against the status quo?” said one well-placed source at the top of the European Commission.

This week the European Council president, Charles Michel, urged politicians to start engaging on EU reforms, setting a 2030 target to be ready for expansion. “There is still a lot of work to do. It will be difficult and sometimes painful. For the future member states and for the EU,” he said.

By how much would the EU budget, currently €186bn, increase? Would the three biggest contributors – Germany, France and Italy – have to dig deeper into their pockets to support Ukraine? Would Poland, which goes to the polls in October, be prepared to shoulder more of the financial burden?

Then there is question of the size of the European parliament. With a prewar population of 44 million, 3 million smaller than Spain and 3 million bigger than Poland, Ukraine might expect between 50 and 60 MEPs. Could it mop up some of the 73 seats left vacant by Brexit? Or would enlargement make parliament unwieldy?  

A spokesperson for the EU said it was “clear that the accession of any new member state has an effect on EU policies, including the Common Agricultural Policy (CAP) and cohesion” funds. They said it was “impossible to comprehensively assess the impact on the CAP or other EU policies” or budgets “prior to the political outcome of the accession negotiations with each candidate country”.