Luke Shaw is on the verge of completing a blockbuster move to Manchester United for around £30m.

The 18-year-old left-back returned from the World Cup on Wednesday and is expected to undergo a medical at Old Trafford today.

If the deal goes through, Shaw will become the most expensive player ever sold by the club.

As revealed by the Daily Echo at the start of the month, the teenager informed Saints after the end of the season that he wished to leave St Mary’s this summer.

United lodged a bid worth a potential £27m immediately following the conclusion of the Premier League campaign, and talks are believed to have taken place between the two clubs during the past few days.

Saints put the issue on the backburner last month, as they resolved their managerial situation, while they also wished to wait until England’s World Cup was over before discussing any possible move.

As previously reported, the club also felt United’s offer did not match their valuation of the player, with the deal’s structure involving far less guaranteed money than the headline figure, with various add-ons included, some of which were never likely to be realised.

However, an agreement last night appeared to have been finalised.

New Saints manager Ronald Koeman was kept informed of issues relating to possible player sales during the process of his appointment, and he will have had full knowledge of any decision to let Shaw go.

Executive director Les Reed, who is the club’s negotiator, has already issued a guarantee that any revenue made from player sales will be reinvested into the squad.

He has also said that the club will only sell players if they feel the fee is right for them and will allow them to improve the team.

It is highly unlikely that all of the money for Shaw will be guaranteed, while payments will probably be spread out over more than one season.

But it will still significantly boost Saints’ budget this summer and, while the departure of a young talent such as Shaw will come as a blow, the additional funds should strengthen Koeman and the club in the transfer market.

If Shaw’s departure is confirmed, attention will then turn to the future of Adam Lallana, who has also informed officials at St Mary’s of his desire to leave.

Liverpool have submitted bids for him on two occasions this summer, although their most recent offer of a potential £25m again fell well short in terms of guaranteed money, with only around £15m thought to have been included up front.

That situation is further complicated by a 25 per cent sell-on clause held by Lallana’s previous club, Bournemouth.

Reed has already said this summer that “Lallana’s been here long enough, we’ve brought him to this level and we feel that perhaps he should give it a little bit longer.”

There is also a sense that, while Shaw’s loss will be a significant one, Lallana’s contribution may be even harder to replace.

Liverpool, who are expected to make another attempt at signing the Saints skipper, will therefore need to increase the value of the deal if they are to persuade the club to part with the 26-year-old England player.

The Reds also want to sign centre-half Dejan Lovren, who, as previously reported, has written to the club requesting to leave.