Mortgage application - gambling transactions

Longer term Pher..Throwaway account. 31yr male. 10 years ago I had a little gambling addiction. Blackjack, poker, sports, trading you name it. Swung between £100k up ('I'm a genius!') and £50k down ('I'm a complete piece of ****!'). Naturally ended up about £40k down after several tumultuous years and thought I'd better sort myself out. Which I did. 10 years later - good job in finance (of all sectors..). Salary of £65k, and I hadn't gambled so much as a penny in nearly a decade.
That was until last week. I had a relapse. It started with a £5 bet on something insignificant. 12 hours later I was £16k down on online blackjack. I guess I could afford it, technically, but it was still an outer body feeling. Clearly the addiction never leaves you, it just lies dormant. Now I know this .. I've put all the measures in place to stop it happening again. Self exclusion from everywhere and so on. Even went to a support group. I'm not looking for advice on this, or any discussion on gambling. My income is fairly high for my age and I just wasted a bunch of it on degenerate activities that I've now vowed to put back in the box they sat for 10 years - permanently. I guess there's a personality flaw in there somewhere (blame the childhood), but I feel I can manage it. Anyway..enough background.
My partner wants to buy a house with me. Jointly we earn £90k and have no debt aside from car leases, so I assume the affordability criteria wouldn't be a problem if we were looking for average priced house of about £300k (N. Ireland, not London..). We have a deposit of £30k lined up. We haven't missed any type of credit payment in years.
But I am worried that my relapse and slew of transactions to various bookmakers over that weekend will cause us a problems during the mortgage application. My partner knows about my past issues but does not know about the recent relapse. She would not be impressed although I might have to come clean....
I've read many banks will ask for 3 months statements and understandably look dimly on gambling transactions, especially ones over £10k! If that's the case, we'd need to wait for at least 4 months before attempting a mortgage application. Is that all I need to be concerned about? Do all banks ask for statements? Do I need 'clean' statements or would I have a chance of getting them past an underwriter because the rest of our application was, in theory, A+? At what stage would bank statements be requested - up front during the AIP stage or only way down the line?
Of course, I would be happy to simply wait 4 months but my partner is super keen to press ahead with an application. Bad timing! Is it own up time or can I squeak it?
Yes I'm a moron.. thoughts appreciated...
TLDR - how do large gambling transactions affect a mortgage application

I can't be of any real help but I did meet the bank earlier last year and it came up in conversation that betting is definitely frowned upon. Too many meals out or visiting the ATM too often were also mentioned which surprised me.

Longer term Pher..Throwaway account. 31yr male. 10 years ago I had a little gambling addiction. Blackjack, poker, sports, trading you name it. Swung between £100k up ('I'm a genius!') and £50k down ('I'm a complete piece of ****!'). Naturally ended up about £40k down after several tumultuous years and thought I'd better sort myself out. Which I did. 10 years later - good job in finance (of all sectors..). Salary of £65k, and I hadn't gambled so much as a penny in nearly a decade.
That was until last week. I had a relapse. It started with a £5 bet on something insignificant. 12 hours later I was £16k down on online blackjack. I guess I could afford it, technically, but it was still an outer body feeling. Clearly the addiction never leaves you, it just lies dormant. Now I know this .. I've put all the measures in place to stop it happening again. Self exclusion from everywhere and so on. Even went to a support group. I'm not looking for advice on this, or any discussion on gambling. My income is fairly high for my age and I just wasted a bunch of it on degenerate activities that I've now vowed to put back in the box they sat for 10 years - permanently. I guess there's a personality flaw in there somewhere (blame the childhood), but I feel I can manage it. Anyway..enough background.
My partner wants to buy a house with me. Jointly we earn £90k and have no debt aside from car leases, so I assume the affordability criteria wouldn't be a problem if we were looking for average priced house of about £300k (N. Ireland, not London..). We have a deposit of £30k lined up. We haven't missed any type of credit payment in years.
But I am worried that my relapse and slew of transactions to various bookmakers over that weekend will cause us a problems during the mortgage application. My partner knows about my past issues but does not know about the recent relapse. She would not be impressed although I might have to come clean....
I've read many banks will ask for 3 months statements and understandably look dimly on gambling transactions, especially ones over £10k! If that's the case, we'd need to wait for at least 4 months before attempting a mortgage application. Is that all I need to be concerned about? Do all banks ask for statements? Do I need 'clean' statements or would I have a chance of getting them past an underwriter because the rest of our application was, in theory, A+? At what stage would bank statements be requested - up front during the AIP stage or only way down the line?
Of course, I would be happy to simply wait 4 months but my partner is super keen to press ahead with an application. Bad timing! Is it own up time or can I squeak it?
Yes I'm a moron.. thoughts appreciated...
TLDR - how do large gambling transactions affect a mortgage application

We've had two applications declined due to gambling transactions...........they looked over the three months statements, totalled the payments, averaged that over three months and inserted that figure into the affordability calculations in the same way as if it was an ongoing loan payment.
If the income had of stood up to that, they would have been accepted but none of them did. The gambling itself isn't a problem........it's the perceived effect of it, if that level of spending continues.
You need professional (mortgage) advice............

Thanks for the info. I'm pretty sure extrapolating 16k a month into continue spending doesn't look so great
This only applies if the '3 months statements' holds though. My colleague through Natwest was only asked to provide last months statement, and her partner as the lead applicant provided 3.
1 months statements and I'm a model citizen :/

Yup, like a specialist broker. My partner is already in touch with one due to the way she is paid with dividends.
I could have the conversation with the broker separately privately, but that seems a little underhand.
I was hoping to avoid having to be in the dog house... wishful thinking perhaps.

I was told similar about gambling, national lottery and other 'non essential' outgoings. Think you may have to sit tight for a bit and come clean which is probably for the best anyway in case she finds out - good luck!

Yup, like a specialist broker. My partner is already in touch with one due to the way she is paid with dividends.
I could have the conversation with the broker separately privately, but that seems a little underhand.
I was hoping to avoid having to be in the dog house... wishful thinking perhaps.

Could you simply show last months statement and the two before that? When I last applied for a mortgage I was supposed to show my last three months statements but couldn't find the February one so gave them Jan March April and they were happy.

Might work... but they're all online these days aren't they?
Could look fishy...

You really want your partner to go into a debt situation with you for the next 25 years plus, but don't want to have to come clean about blowing £16k?
How would you feel if you found she/he (sorry no idea as to your persuasion) hadn't been truthful with you and had locked you into a 25 year debt?
If you have any sort of humanity you should come clean and let them decide if they want that risk.

Well - humanity might be a little harsh.. but I am inclined to agree with you.
However we are not talking about saddling my partner with a load of debt here - I have no debt. Mortgage payment would only represent 25% of our monthly income. Notwithstanding the issue described we'd probably sail through a mortgage application.
I would describe it as one lapse in judgement in an otherwise clean as a whistle 10 year period. I (would like to) think that is different from a period of ongoing degenerate gambling, landing oneself into debt. But hey, maybe I'm kidding myself. It's more the disappoint for her I was trying to avoid. As a man I was aiming for the least hassle option, you can understand that

Yup, like a specialist broker. My partner is already in touch with one due to the way she is paid with dividends.
I could have the conversation with the broker separately privately, but that seems a little underhand.
I was hoping to avoid having to be in the dog house... wishful thinking perhaps.

Suppose the OP was up 16k instead of down. How might that affect the application?

Go for the dog house. She's about to make a big financial joint decision and ought to know.
And by the time she's calmed down and finished shouting the 4 months will have flown by and you'll be ready to make the applications.

Suppose the OP was up 16k instead of down. How might that affect the application?

From what I have read it would obviously not be treated as income, but it wouldn't be perceived too negatively. People win the odd accumalator don't they. Don't think that could penalise.

Will do...

Any need to avoid his existing bank i.e. could they look back further than 3 months internally?